Brief update: if I disconnect the battery, and then reconnect it, the dashboard lights will come on! But then, when I turn the key, the car won't start. I don't hear any response at all, the starter motor doesn't make a sound. Then, when I turn the key again, all the dashboard lights go out. There's no power, whatsoever.

 

Go to your local autoparts store and have them load test the battery. Sounds to me like you have a dead cell. Even with a dead cell, a battery WILL hold a charge. Did you clean the posts and clamps when you installed the new ones. If not, get yourself a post/terminal cleaner while at the parts store and try shining both up. You may be surprised!

 

Ahhhh, a little more information. Try lightly tapping the starter with a hammer and then try starting it. The bendix could be stuck in the teeth on the torque converter.

 

Welcome to Allpar. Try moving the shift lever from P to N & then try cranking it over? Does the PRNDL box follow which gear range is selected?
Do the headlamps come on & do they dim at all when you try to start it?

 

When I reconnect the battery, the odometer lights on the dashboard come on. I insert the key and turn it to the second position, and the other dashboard lights come on. Then I turn the key to the third position, and nothing happens. So, I return the key to the first position and try to start the car again. This time the miscellaneous dashboard lights do not come on when the key's in the second position, although the odometer lights do. Again, nothing happens in the third position. And when I try it a third time, the odometer lights go out with the key in the third position.

I was thinking, maybe there's a short at the starter? Could that be a possibility? But why would it start doing this when the battery's negative terminal cable connector broke? I like the thought of a dead cell in the battery, better--I have no idea how old the battery is, at least a couple years. It seems reasonable that it would hold enough of a charge to power the lights, but not enough to turn the starter.

Thank you, chuzz and ImperialCrown! I'll look into getting my battery tested and/or replaced, and I'll tighten the main battery cable at the TIPM.

 

Welcome aboard.
Possible ans: burned/shorted ignition switch cylinder/contacts. How many miles are on this odometer? If it's very high, suggest troubleshooting the ignition switch.
Once isolated, it was an easy fix & my OEM stamped steel battery clamp was also in terrible condition (40% of it eroded-away, but no cracks noted), & this flaw never caused any known issues.
Afterwards, (at the behest of my mechanic) I did remove all other keys from the PTs ring: 19 years x 16 more brass keys added-up to some unnecessary cylinder wear & tear.
G' luck, & YMMV.

Again, nothing happens in the third position. And when I try it a third time, the odometer lights go out with the key in the third position.
But why would it start doing this when the battery's negative terminal cable connector broke?

 

But, then again, on second thought, the car wouldn't power up when AAA tried to jump-start it. This seems to indicate that something other than the battery is at fault, right?

 

The TIPM distributes power to other circuits. Make sure everything is plugged in. Look for corrosion or loose connections.
Do wiring wiggle tests. Try a 'fist thump' on top of the dash, above the instrument cluster.

 

. . . .The TIPM distributes power to other circuits. Make sure everything is plugged in. Look for corrosion or loose connections. Do wiring wiggle tests. Try a 'fist thump' on top of the dash, above the instrument cluster. . . . .

The TIPM powers all the circuitry within the vehicle. Besides power feed, check ground for the TIPM. G102 is ground for the TIPM and is located inner left fender area. See attached image.

 

Thank you, I'll do all that. Stay tuned...

 

If that one cable connection at the TIPM is compromised, just about everything in the car will be cattywompus. And I, too, have had a stamped factory battery clamp crack.

 

There are less than 140k miles on the odometer. I can't give you the exact number because the odometer won't light up anymore, but it was 139-something when it lit up last.

I disconnected the battery this afternoon--and noticed, to my surprise, the positive battery terminal had become seriously corroded! Wow, I had just cleaned that a couple days ago, and the car hasn't been running. That seems like a symptom of...something. (The negative terminal was clean and shiny.)

I pulled the battery out of the car, and cleaned the positive terminal (again). I checked the ground connections, G102, the ground for the TIPM, and the ground for the battery that connects to the car body. They seemed tight; but I loosened them, cleaned them, and re-tightened them. I pulled out the TIPM, and checked for loose wires or connections, and found none. The positive battery cable connection to the TIPM seemed tight, as well; but I removed it, found no corrosion, and re-tightened it. Then I put everything back into place.

As I had hoped, when I opened the car door and looked at the dashboard, I saw that the lights had come on! (I really should have checked the odometer reading, but it slipped my mind :$

My idea was this: perhaps, when I had tried to jumpstart it previously, it was in its lockdown mode, with no dashboard lights lit. And perhaps, in this lockdown mode, it couldn't make a connection to the starter. But if I jump it now, when it has just enough juice to light the dashboard, maybe it'll fire up the starter motor! So that's what I tried: I hooked up jumper cables from my girlfriend's van to the battery in my car, ran the motor in the van for five minutes, and then tried to start my car.

Again, the odometer lights came on when I opened the door, the miscellaneous dashboard lights came on when I turned the key...and everything went dead when I tried to engage the starter. That suggests to me there's a short at the starter. But I suppose it could be a short in the ignition switch. Or, it could be a problem in the TIPM (This vehicle has had intermittent "limp mode" issues; my solution has been to shut off the engine and re-start it; that works every time.)

It looks to me as though the only cure for this problem is to take the car to a repair shop, and pay them to experiment with it until they find the solution--or don't find any solution, as the case may be. What I oughta do is buy a different car, but I can't exactly afford to do that. Any thoughts would be appreciated! And I'll keep you all updated as to the status of this ongoing crisis

 

. . . .I pulled the battery out of the car, and cleaned the positive terminal (again). I checked the ground connections, G102, the ground for the TIPM, and the ground for the battery that connects to the car body. They seemed tight; but I loosened them, cleaned them, and re-tightened them. I pulled out the TIPM, and checked for loose wires or connections, and found none. . . . .

Did you clean ground G100? It connects the battery negative terminal to the car body.

. . . .As I had hoped, when I opened the car door and looked at the dashboard, I saw that the lights had come on! (I really should have checked the odometer reading, but it slipped my mind :$ . . . .

Some electrical current is travelilng from the battery to the instrument cluster. Good sign.

. . . . My idea was this: perhaps, when I had tried to jumpstart it previously, it was in its lockdown mode, with no dashboard lights lit. And perhaps, in this lockdown mode, it couldn't make a connection to the starter. . . . .

Interesting theory but the security system nor any other module behaves in this manner. So you need to do more diagnostics.

. . . . But if I jump it now, when it has just enough juice to light the dashboard, maybe it'll fire up the starter motor! So that's what I tried: I hooked up jumper cables from my girlfriend's van to the battery in my car, ran the motor in the van for five minutes, and then tried to start my car.

Again, the odometer lights came on when I opened the door, the miscellaneous dashboard lights came on when I turned the key...and everything went dead when I tried to engage the starter. That suggests to me there's a short at the starter. But I suppose it could be a short in the ignition switch. Or, it could be a problem in the TIPM (This vehicle has had intermittent "limp mode" issues; my solution has been to shut off the engine and re-start it; that works every time.) . . . .

It is possible that there still is a poor electrical connection in the starter control and / or starter engagement circuit that is causing the problem. Also you could have a battery with a weak cell. It can power interior lights and the instrument cluster but when requested to supply 150 - 200 amps to operatre the starter it goes dead. Even with jumper cables connected to the Cruiser battery from another vehicle, it will still behave with no starter operation if it has a weak cell.

. . . .It looks to me as though the only cure for this problem is to take the car to a repair shop, and pay them to experiment with it until they find the solution--or don't find any solution, as the case may be. What I oughta do is buy a different car, but I can't exactly afford to do that. . . . .

Do NOT give up on this car. Try this test.

The attached schematic diagrams show the location of the starter relay and wiring from the starter relay and direct power feed to the starter solenoid. Unplug the starter relay. Make sure the transmission is in PARK or NEUTRAL and parking brake firmly applied. This test bypasses the neutral start safety switch and can cause the engine to start and vehicle run away. Set ignition switch to OFF position.

Using the diagram for the starter wiring connect a suitable jumper wire between terminal #30 and #87 at the starter relay connector. Do NOT touch #85 or #86. The starter should engage. Report your test results. This test bypasses ignition switch, neutral start safey.

 

So, the short answer is...the test proved negative. The starter did not engage when I bypassed the start safety switch.

The slightly longer explanation is this. There's a metal bracket holding the two relay housings. I unbolted this bracket from the firewall, which allowed me get an easier grip on the starter relay. With the aid of a flat head screwdriver, I gently pried the two halves of the relay housing apart.

Then I reconnected the battery, and put the air intake apparatus back into place. Next I inserted one end of a 12 gauge wire into cavity #30, and the other end into #87. Nothing happened, as a result.

This would seem to indicate that the problem is in the starter, no? But that doesn't explain why my instrument panel no longer lights up. (The symptom's sure do seem like a dead battery--too bad it proves good on all the tests

PS: Yes, I have checked all the fuses in the TIPM--visually, at least. None of them appear to be blown, but I don't know for certain that they will all pass electrical current.

 

. . . . So, the short answer is...the test proved negative. The starter did not engage when I bypassed the start safety switch. . . . .

.Then I reconnected the battery, and put the air intake apparatus back into place. Next I inserted one end of a 12 gauge wire into cavity #30, and the other end into #87. Nothing happened, as a result.

This would seem to indicate that the problem is in the starter, no? But that doesn't explain why my instrument panel no longer lights up. (The symptom's sure do seem like a dead battery--too bad it proves good on all the tests - - -

Not correct. This test indicates that there is no power at cavity #30. In post #14, dated Aug 19, 2023, I indicated to set the ignition key switch in the OFF position. I assumed cavity #30 would always have direct battery power. That may have been an incorrect assumption on my part; my error.

Repeat your test with a jumper wire between cavity #30 and cavity #87 at the starter relay connector. Have a helper turn the ignition key switch to the START position and hold. Does the starter engage? If it does not engage there is no power between terminal #8, connector C10 at the TIPM and cavity #30 at the starter relay on the YL/TN wire. More diagnosis necessary.

. . . . Yes, I have checked all the fuses in the TIPM--visually, at least. None of them appear to be blown, but I don't know for certain that they will all pass electrical current. . . . .

You can always substiitute another 10 amp fuse found in the fuse box for #4 fuse.

 

Well, I tried it. I repeated the test with the jumper wire between #30 and #87, and had the ignition key turned to the START position...and nothing happened.

Of course, this wasn't entirely surprising, as there's no indication of power anywhere from inside the car. No "door ajar" indicator, no interior lights, no odometer reading, no power locks or windows, and no dashboard lights.

Sign. It would have been so simple if it had just been a dead battery! Guess I'm just gonna have to have AAA tow it to an auto shop. I greatly fear that the repairs will cost more than the car is worth.

But thanks for everyone's help! I'm grateful for your advice, AllanC

 

. . . .Well, I tried it. I repeated the test with the jumper wire between #30 and #87, and had the ignition key turned to the START position...and nothing happened. . . . .

I can understand your frustation but I am thinking we are very close to a solution.

What is known. No illumination of the instrument cluster. Bypassing to get direct activation of the starter solenoid from the TIPM gives no action. So that means the TIPM is not receiving power.

See attached image. Part of the TIPM receives unswitched, constant power through fuse #4 in the fuse box. The ignition key switch receives power through fuse #4. Part of the TIPM receives power through the ignition switch RUN and START positions. You have visually inspected but no assurances that the fuse is good and will pass electrical current. Also there is a direct cable from the positive battery post to the underneath side of the TIPM fuse box. It must be clean and tight. You would need to unbolt the TIPM, invert it and check the electrical cable attachment point. See attached image.

. . . . . . . . Guess I'm just gonna have to have AAA tow it to an auto shop. I greatly fear that the repairs will cost more than the car is worth. . . . .

You cannot base your decision on residual salvage value of the vehicle. You need to look at what it would cost to replace your ailing PT Cruiser with a like automobile. What is the overall conition of the vehicle? If you make that comparison then a few hundred dollars in repairs are less than a replacement vehicle.

I will reiterate that I believe the solution is very close at hand. But at this point you will need some more test equipment to proceed. You will need a 12 volt test light and / or a multi-meter to measure for power on circuits and circuit resistance / continuity. With a multi-meter or test light you can quickly determine if fuse #4 is good and if you are getting power to the TIPM on that connection on the underneath side.

I am still willing to work with you to solve this problem. Review the attached diagrams and then evaluate whether you want to invest and learn how to use a test light and multi-meter. I will respect your decision.

 

AllanC knows his stuff, man. Just hang in there with him and he'll most likely figure it out. You can get both a test light and a multi meter at Harbor Freight for less than $20. That's where I got mine.

 

Thank you, AllanC! I am hoping to repair this vehicle for only a few hundred dollars--I am definitely willing to invest and learn to use a test light and multi-meter. My only fear is that I have exhausted my limited mechanical abilities. I've made an appointment to drop off the car in a week at a repair shop; it'd be amazing if I could repair it myself before then!

As a matter of fact, I do have a multi-meter--or, access to one, at least. The attachment of the direct cable from the positive battery terminal to the TIPM is clean and tight. I've detached it, checked for corrosion, and firmly reattached it.

I'll check fuse #4 with the multi-meter to determine whether it's any good just as soon as I can!

Cheers,
Theo

 

. . . .As a matter of fact, I do have a multi-meter--or, access to one, at least. The attachment of the direct cable from the positive battery terminal to the TIPM is clean and tight. I've detached it, checked for corrosion, and firmly reattached it. . . . .

So you removed the TIPM, inverted it and checked the battery cable terminal on the underneath side of the TIPM? You cleaned it and reattached firmly?

. . . .Yes, the #4 fuse is good. I tested the continuity of the circuit with my meter. . . . .

Very good. Another potential trouble spot eliminated.

. . . .The next step is, what, to test whether I'm getting power to the TIPM through the cable to the positive battery terminal? I'm fairly confident that I am. The cable appears undamaged, the connection is solid, and the battery has been tested-- . . . .

A cable could have internal corrosion damage (under the outer sheath) such that it will show voltage potential on a multimeter but not be able to provide substantial amperage to operate electrical devices.

. . . . But it's getting late, and I think I'll wait till tomorrow morning before I test the current draw there. . . . .

You should NOT use a multimeter to test for amperage draw on an electrical circuit. Unless you know absolutely that the circuit is only drawing milliamps then you can put the meter in series with the circuit and measure amperage. Too many amps through a multimeter can damage the device. A safer solution is to use a test lamp that draws 1 - 2 amps and places a load on a suspect circuit. If the bulb illuminates brightly, then you can assume the circuit is good and does not have excessive resistance. So let's put an amperage draw test on the sideline for now

Before moving on to test the output of the ignition switch, try this test. The video link shows wiggling all the four connectors at the PCM. Do this wiggle test and see if that solvles the problem.

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. . . .In the event that there is power going to the TIPM, what would that tell us? Perhaps that the TIPM has failed and needs to be replaced? . . . .

A TIPM can fail but electronics are very reliable. So more testing is required before condemning the TIPM.

. . . Or, on the other hand, what if there is no power going to the TIPM? What would that mean? That the circuit is incomplete, yes. Either the battery isn't functioning, despite the test results, or the positive cable and connection is flawed, or the TIPM ground connection is flawed. . . . .

No constant battery power going to the TIPM or a poor connection that will not support 8 - 10 amp circuit draw can cause a problem. Post #10 dated Aug 16, 2023 shows the location of ground G102 for the TIPM. You inidcated that you cleaned that connection. Post #14 dated Aug 19, 2023, shows the location of ground G100 which provides all the grounds for the TIPM. There are multiple ground circuits for the TIPM and they all end in eyelets stacked at location G100. In post #15 you indicated you cleaned it.

. . . . You know, now that I think about it...I checked the ground connection to the body of the car, but I didn't check the connection to the TIPM, itself. That might be something to look at--assuming, of course, that there is no power going to the TIPM, when I check it tomorrow morning. . . .

First statement in this thread asks if you inspected the power cable feed on the underneath side of the TIPM.

 

Yes, the #4 fuse is good. I tested the continuity of the circuit with my meter.

The next step is, what, to test whether I'm getting power to the TIPM through the cable to the positive battery terminal? I'm fairly confident that I am. The cable appears undamaged, the connection is solid, and the battery has been tested--although, of course, it could be that the TIPM ground connection isn't as good as I thought it was, right? But it's getting late, and I think I'll wait till tomorrow morning before I test the current draw there.

In the event that there is power going to the TIPM, what would that tell us? Perhaps that the TIPM has failed and needs to be replaced?

Or, on the other hand, what if there is no power going to the TIPM? What would that mean? That the circuit is incomplete, yes. Either the battery isn't functioning, despite the test results, or the positive cable and connection is flawed, or the TIPM ground connection is flawed. You know, now that I think about it...I checked the ground connection to the body of the car, but I didn't check the connection to the TIPM, itself. That might be something to look at--assuming, of course, that there is no power going to the TIPM, when I check it tomorrow morning.

Thanks again!

 

Thanks for the warning about testing the amperage draw with a multimeter! I do believe there's a test lamp out at my girlfriend's apartment, so I'll go grab that tomorrow and test the amperage draw then.

I went ahead and tried the wiggle test on the four connectors at the PCM. There was no change in the status quo, the car remained without power.

Next, I should test the output of the ignition switch? Ok, I'll try that. But, you know, I don't think the ignition switch is getting any input, considering that no of the dashboard lights have power. Or, is the ignition independent of all that?

 

. . . .Thanks for the warning about testing the amperage draw with a multimeter! I do believe there's a test lamp out at my girlfriend's apartment, so I'll go grab that tomorrow and test the amperage draw then. . . .

As a sideline a test light that draws 1 - 2 amps is a good tool for placing an electrical load on a circuit. If you get bright illumination the circuit is good and low resistance. But you have to be careful and be knowledgeable when testing electrical circuitry.

When testing the output of a solid state module such as a PCM, you should use an LED test lamp. An LED test light only draws a few milliamps. Reason is that a regular test light with incandescent bulb can place an excessive load on a solid state circuit designed only for a few milliamps of current. Solid state circuits that power and control relays typically only see milliamps of current. You can permanently damage a solid state circuit by connecting a device with a few amps of current draw. Chrysler designed solid state circuits typoically have overcurrent protection built into the solid state device drivers. The circuit logic detects the over current and disables the circuit. But it is best to NOT rely on logic to protect from damage. So you need to know the circuit you are testing and consult a wiring diagram before doing this type of electrical testing.

. . . .I went ahead and tried the wiggle test on the four connectors at the PCM. There was no change in the status quo, the car remained without power. . . . .

Another possible problem area eliminated.

. . . .Next, I should test the output of the ignition switch? Ok, I'll try that. But, you know, I don't think the ignition switch is getting any input, considering that no of the dashboard lights have power. Or, is the ignition independent of all that? . . . .

Yes, the next area to diagnose and address is the input and outputs at the ignition switch. However have you checked the battery cable eyelet connection on the underneath side of the TIPM? I presented a picture of that in post #24. I am NOT referencing the cable clamp at the positive battery post. You have already checked and cleaned that area.

I will work on assembling some diagrams and test procedures for ignition switch. Accessing the ignition switch is somewhat of a challenge.

 

So, this morning, I pulled out the TIPM again. I verified that all the wires on the underside are securely plugged into their sockets, and that none of them are missing or frayed. I detached the positive battery cable from the underside of the TIPM (it was already detached from the battery), and tested it for continuity. (I figured that'd be easier than riding my bike out to my gf's place and getting the test light.) The positive cable is good. The ground connections at the TIPM appear to be good, as well; and G100 battery ground to fender, G101 to the starter, and G102 to left strut tower are all clean and tight.

Looking forward to test procedures for the ignition switch!

 

. . . So, this morning, I pulled out the TIPM again. I verified that all the wires on the underside are securely plugged into their sockets, and that none of them are missing or frayed. I detached the positive battery cable from the underside of the TIPM (it was already detached from the battery), and tested it for continuity. (I figured that'd be easier than riding my bike out to my gf's place and getting the test light.) The positive cable is good. The ground connections at the TIPM appear to be good, as well; and G100 battery ground to fender, G101 to the starter, and G102 to left strut tower are all clean and tight. . . . .

Good chekcout. So another problem area, power at the underneath side of the TIPM, can be eliminated.

Let’s check to see if there is 12 volt power at connector C104 under the dash driver side. Power travels from fuse #4 at TIPM, through connector C104 to terminal #5 at the ignition switch. See attached image for location of connector C104. You may have to remove a trim panel under the dash and steering column.

Separate the connectors at C104. On the side with wire color PK/DB, pin or cavity #42, back probe and insert a paper clip in #42. I am having you do a back probe instead of touching your test light to the mating area. Pins and cavities are very small and it is all too easy to accidentally short #42 against an adjacent pathway. Pin or cavity #42 should have full time power (not switched). Touch test light to back probe pin and other lead of test lamp to steering column for ground. Does it illuminate? If NO then there is a problem with this PK/DB wire from connector C104, through the firewall and into the TIPM at fuse #4.

If YES then there is power to connector C104. Reattach the male and female components of the C104 connector. Back probe on the C104 connector the RD wire at pin or cavity #42. Repeat touching test lamp to probe and ground. The test lamp should illuminate indicating 12 volt power is going through the C104 connector. Does the test lamp illuminate?

If test lamp illuminates at #42 on the RD wire, time to move onto the ignition switch.

This is a video link that shows gaining access and removing the ignition switch on a 2004 PT Cruiser which will be the same for a 2006 model. You will need a tamper proof TORX bit set with recessed dimples in the bit end to remove the screws.

You many have to separate the electrical connector at the ignition switch to free it from its mounting. Once free reattach electrical connector to ignition switch. Image below shows the pinouts at the 5 pathway electrical connector at the ignition switch.

As a double check for safety, make sure transmission in PARK and parking brake firmly engaged. You do NOT want the engine to inadvertently start during this test procedure.

For these tests you will need to back probe the appropriate path in the connector. Use your test lamp and check for power on #5 cavity? Use a screwdriver and turn the ignition switch to the ON / RUN position. Use test lamp. Should be power on #3 cavity? Use screwdriver and turn ignition switch and hold in START position. Should be power on #3 amd #4 cavity? Report your findings.

 

Thanks! I'll check on connector C104 this morning. (My dashboard lights are back on! The odometer reads 139421.)

 

. . . .Thanks! I'll check on connector C104 this morning. (My dashboard lights are back on! The odometer reads 139421.) . . .

Do you see the P R N D indicator above the odometer window display? Is there a box around the P indicating the transmission selector is in PARK position? See attached image.

 

The P R N D indicator does not light up without the key in the ignition and turned to the 2nd position--and when I turn it to the 3rd position, engaging the starter, the whole system goes dead. So, I've shied away from putting the key in the ignition. The only lights that came on with the door opened were "door ajar" and the odometer lights.

Then, before I started removing trim panels this morning, I decided to disconnect the battery in order to avoid accidentally triggering the airbag. And it was a good thing that I did this, I think; as I uncovered what certainly looks like an airbag--even though I thought the airbag was in the steering wheel.

But I can definitely hook up the battery and turn the key to the 2nd position, if you think that'd provide useful information!

I've removed a couple panels and gained access to the area under the steering wheel. I am having trouble, however, making sense of the attached image you kindly provided and correlating it to what I see under the dash. I have 2 connectors just behind the OBD output, one is black and one is white. These could possibly be C104 and C105, but I'm not sure which is which. Do you know where I could find that information? Is there a good PT Cruiser repair manual that I could download? (Chilton's print manual is inadequate.)

Thanks for your help!

 

. . . . The P R N D indicator does not light up without the key in the ignition and turned to the 2nd position--and when I turn it to the 3rd position, engaging the starter, the whole system goes dead. So, I've shied away from putting the key in the ignition. The only lights that came on with the door opened were "door ajar" and the odometer lights. . . . .

The instrument panel receives power through the igntion key switch when it is in the RUN and START positions. It also receives direct (unswitched) power through another circuit. Since the DOOR AJAR and odometer display illuminates when the door is opened, that means the unswitched feed circuit is alive and well. I am starting to suspect the ignition switch is the culprit but more testing is needed.

. . . . Then, before I started removing trim panels this morning, I decided to disconnect the battery in order to avoid accidentally triggering the airbag. And it was a good thing that I did this, I think; as I uncovered what certainly looks like an airbag--even though I thought the airbag was in the steering wheel.

I did research and it appears the 2006 model PT Cruiser has a knee bolster air bag restraint. The video link in post #28 showing access to the ignition switch is a 2004 model. In 2004 the air bag knee bolster was probably not standard issue. In case of severe collision and air bag deployment, the knee bolster tends to keep the driver from "submarining" under the steering wheel air bag.

. . . .I've removed a couple panels and gained access to the area under the steering wheel. I am having trouble, however, making sense of the attached image you kindly provided and correlating it to what I see under the dash. I have 2 connectors just behind the OBD output, one is black and one is white. These could possibly be C104 and C105, but I'm not sure which is which. . . . .

In writing post #28 I intended to include the pinout diagram for the 43 pathway C104 connector. But in review I find that I forgot to include it. It is attached below. C105 connector has 16 pathways so the difference is obvious.

At connector C104 look for the side of the male and female components of the connector that has a PK/DB wire in position #42. That is the power feed from fuse #4 at the TIPM.

. . . .PS: Yes, the P R N D indicator illuminates with the key in the 2nd position, and there is a box around the P indicating the transmission selector is in PARK position! . . . .

More valuable information. Because the P R N D display has a box around the P, we know that the PCM is receiving a proper signal from the TCM (transmission control module) part of the PCM that the transmission selector is in PARK position. The PCM sends this information over the network to the instrument cluster and the instrument cluster displays the transmission selector position. This is critical because the PCM controls the ground side of the starter relay control circuit. Attached is a snipet of the starting circuit from post #14, dated August 18, 2023.

 

PS: Yes, the P R N D indicator illuminates with the key in the 2nd position, and there is a box around the P indicating the transmission selector is in PARK position!

 

You may also have SRS airbags in the front seats & upper B-pillars.

Because the system goes dead when moving the key to the 'start' position, it almost sounds like a poor connection with high-resistance that opens when under a load.
The ignition switch doesn't carry large amounts of current. It is more of a 'sense' switch, the TIPM does the heavy switching-work.

 

UPDATE: I've managed to start the car!!

I repeated the start safety switch bypass test. With a jumper wire between terminal #30 and #87 in the starter relay, I turned the key in the ignition and the car started, no problem.

I retried this test because separating the male and female components of C104 was proving difficult. I paused to rest, and I got to thinking. All my dashboard and interior lights are working...this wasn't the situation when I'd initially tested the safety switch bypass...maybe it'll get power now, that it wasn't getting earlier...?

And, sure enough, that seems to have been the case. My next thought is...well, if it started with a jumper wire between #30 and #87, will it start without a jumper wire there? Or, would trying that be jinxing things?

What does this successful test indicate? This means that "... the starter, starter relay, and wiring from the positive battery terminal is good and wiring from the starter relay to the starter solenoid is good." It also indicates that there's nothing wrong with the ignition switch.

So, why would the whole electrical system go dead, when I turned the key to the "start" position? That's how this whole adventure began. It was apparently triggered by a broken negative battery terminal clamp, which has subsequently been replaced.

Should I try to start the car without the safety switch bypass? In the hope that the initial problem just sort of went away? I'm nervous about doing that. But I can't drive it, of course, with the jumper wire in place; and what are the other options? What further diagnostic checks can I make?

Thanks again!!

 

. . . . UPDATE: I've managed to start the car!!

. . . . I repeated the start safety switch bypass test. With a jumper wire between terminal #30 and #87 in the starter relay, I turned the key in the ignition and the car started, no problem. . . . .

. . . . And, sure enough, that seems to have been the case. My next thought is...well, if it started with a jumper wire between #30 and #87, will it start without a jumper wire there? Or, would trying that be jinxing things?

. . . . What does this successful test indicate? This means that "... the starter, starter relay, and wiring from the positive battery terminal is good and wiring from the starter relay to the starter solenoid is good." It also indicates that there's nothing wrong with the ignition switch. . . . .

. . . . So, why would the whole electrical system go dead, when I turned the key to the "start" position? That's how this whole adventure began. It was apparently triggered by a broken negative battery terminal clamp, which has subsequently been replaced. . . . .

This entire frustrating fiasco of NO START was caused by the ignition switch and excessive electrical resistance. Chrysler engineering specifices to its suppliers of electrical components / switches (as do all other manufacturers) to add a small amount of dielectric grease to the internal, mechanical switch contact points. Idea is to reduce corrosion on the contacts and potentially eliminate a no current circuit situation. This works quite well in the short term (gets the vehicle past the initial 3 / 36 manufacturer warranty) but causes problems in the longer term.

I have seen this problem on Chrysler vehicles and with switches on GM vehicles. In fact I experienced no starter operation on my 2016 Jeep Patriot when it was only 2 years old. Fortunately I was able to bypass the ignition key switch starter operation because the Patriot has a remote start feature which bypasses the ignition key switch operation. Your PT Cruiser does NOT have that feature.

At this point you can remove the ignition switch, open the case and clean the contacts. Or you can replace the entire assembly.

Attached are diagrams which show the ignition key switch for a 2016 Jeep Patriot. The ignition switch in your PT Cruiser will be very similar if not identical. You can see how dielectric grease over time will attract dirt and other debris which can eventually interfere with adequate electrical current passage bewteen the RUN circuit contacts and the START circuit contacts.

One other item to check. In the diagrams you see how the actuator extension metal device mates to the actuator receptacle made of plastic. Make sure that turns correctly when the ignition key switch is turned in the lock. If that actuator extension is broken it could cause an intermittent, mechanical situation where the key is turned but the switch is not rotated.

 

To make sure the battery isn't being pulled down, or the ignition switch is bad, remove the bypass and have someone measure the battery voltage while you hold the key in the start position. That tells whether there is a short or dying battery (battery voltage would plunge), or whether there is an open circuit (battery voltage remains unchanged around 12.4 to 12.6 volts).

 

Or, could it mean that the relay is bad? Considering that the car will start when I bypass the relay, that would seem to make sense--except, when I test the relay with my multimeter, it checks out.

So, what does that mean? If the relay is good, and the car will start with a jumper between cavity #30 and #87, then it should start with the jumper removed and the relay back in place, right?

Except, the last time I tried to start it with the relay in place, the whole system died. But...if I have someone measuring the battery voltage while I try to start the car, then I have a dying battery or an open circuit. And that would be useful information.

Wait, though, the car started just fine with a jumper wire bypassing the relay! Surely that indicates that neither is the battery dying nor is there an open circuit. Right?

I think I should just put the relay back in place and try starting the car. What have I got to lose?

 

Or, could it mean that the relay is bad? Considering that the car will start when I bypass the relay, that would seem to make sense--except, when I test the relay with my multimeter, it checks out.

So, what does that mean? If the relay is good, and the car will start with a jumper between cavity #30 and #87, then it should start with the jumper removed and the relay back in place, right?

Except, the last time I tried to start it with the relay in place, the whole system died. But...if I have someone measuring the battery voltage while I try to start the car, then I have a dying battery or an open circuit. And that would be useful information.

Wait, though, the car started just fine with a jumper wire bypassing the relay! Surely that indicates that neither is the battery dying nor is there an open circuit. Right?

I think I should just put the relay back in place and try starting the car. What have I got to lose?

No, pins 30 and 87 are the load side of the relay. You jumped battery power across. If the relay tests good with the multimeter, but you have to remove it and bypass it to start, that tells me that the computer is not turning on the relay (at pins 86 and 85 of the relay), or, maybe less likely, the wiring to the coil side of the relay is damaged. So, no, plugging the relay back in won't necessarily allow it to start.

 

Yes! The car started with absolutely no hesitation.



Does anyone have an idea as to why this all occurred? I'd like to keep it from happening again, you see; but I can't make sense of how it happened--or what fixed it.