[AllanC]

. . . When I started this today I had the dead short on the map sensor until I unplugged the TPS and it went away. After inspecting wires now the dead short wont return but I am showing 5 ohms which disappears when I unplug the TPS. I checked the 5V to ground on the new and the old TPS and they both measure 5 ohms. . . . .

See attached image. From your description it appears there is a short between the signal wire terminal and the sensor ground terminal; #2 and #3 in the diagram.

. . . Should I be reading this resistance across the TPS? . . .

See notes on attached image.

 

[Lcattin]

Between 1-3 I have a constant .48 ohms
Between 1-2 I have a decrease from 4.88K - 360 ohms
Between 2-3 I have an increase from 62 ohms - 4.6K

No zero's anywhere.

 

[ImperialCrown]

0.48Ω would effectively be 0Ω.
The signal terminal should be from the wiper of the potentiometer as it varies with throttle opening. The 5 volts to ground potential is distributed across the TPS resistance shoe.

 

[Lcattin]

sorry the first should have read 5 ohms

 

[Lcattin]

Just discovered that my injectors are now firing but I'm still looking for spark.

 

[AllanC]

. . . . I started digging into the wiring harness. I separated a number of wires that were stuck together but didn't appear to be melted.

When I started this today I had the dead short on the map sensor until I unplugged the TPS and it went away. After inspecting wires now the dead short wont return but I am showing 5 ohms which disappears when I unplug the TPS. I checked the 5V to ground on the new and the old TPS and they both measure 5 ohms. . . . .

You need to return to the area of the wiring harness that had wires stuck together. By separating them I believe you might
have eliminated the problem with a wiring power to ground short. Wrap each wiring area individually with tape that was fused. You do not want this to happen again.

. . . Between 1-3 I have a constant .48 ohms
Between 1-2 I have a decrease from 4.88K - 360 ohms
Between 2-3 I have an increase from 62 ohms - 4.6K

No zero's anywhere. . . . .

. . . sorry the first should have read 5 ohms . . .

I believe you have eliminated the TPS as a cause for the short in the wiring.

Check the 3 MAP sensor terminals for resistance between each pin in turn and report your findings. See attached image.

 

[Lcattin]

Map sensor looks good. I measured resistance in all pin combinatons.

I was checking the ignition coil circuity and the asd relay is not being activated by the ECM to provide 12V to energize the coil. I ran the wiring to the ECM plug and it is good. I have continuity all the way to the ECM connector. With what I a have read I should have 12V to the coil with the key turned on. Is this correct?

 

[AllanC]

. . . . Map sensor looks good. I measured resistance in all pin combinatons. . . . .

OK. You can rule out the MAP sensor as the source of the problem.

. . . .I was checking the ignition coil circuity and the asd relay is not being activated by the ECM to provide 12V to energize the coil. I ran the wiring to the ECM plug and it is good. I have continuity all the way to the ECM connector. With what I a have read I should have 12V to the coil with the key turned on. Is this correct? . . . .

The PCM only energizes the ASD and fuel pump relay if it receives a valid signal from the crankshaft position sensor that the crankshaft is rotating. So with key ON / RUN position but starter not engaged there will be no electrical power flow through the load side of the relay. This is a safety feature built into the PCM logic.

Try this test. Swap the ASD relay with the starter relay in the PDC. Engage the starter. See attached image. It is possible that there was a short in the wiring harness that you previously found and have inadvertently corrected. It is possible that the load side contacts are burned / pitted in the ASD relay and are now not providing adequate current flow to the fuel injectors and coil.

 

[Lcattin]

I plugged everything back in and swapped the relays.

I also checked the coil while cranking and the ASD was supplying the voltage as you stated it would.

I back probed the 5V supply to the MAP sensor and it was a steady 5V while cranking.

I'm still getting P0122, P0117, P0107 and P1192

The codes were clear when I started today as the battery was disconnected.

Thanks for the help as I really appreciate it.!

 

[AllanC]

. . . I plugged everything back in and swapped the relays.

I also checked the coil while cranking and the ASD was supplying the voltage as you stated it would.

I back probed the 5V supply to the MAP sensor and it was a steady 5V while cranking. . . . .

OK. ASD relay is good and will pass adequate electrical current to fuel injectors and coil.

You need to check for 12 V power at fuel injector harness and at the coil. See attached image. CAUTION: use a test light with an LED bulb. Test lights with an incandescent bulb can draw 1 - 3 amps and this can damage control circuits in the PCM.

Check for 12 V power while engaging starter. Then check the PCM control circuits to the fuel injectors and coil. If you do not see a pulsing lamp when checking the control circuits then the PCM has failed and will need to be replaced.

Here is a video that shows how to use a test light to check pulsing at the fuel injector. Vehicle is a Honda but the principle shown is for many vehicles.

View: https://www.youtube.com/watch?v=pzeOz-seIQE


At time interval 5:40 the presenter shows how to check for proper voltage at the fuel injector harness. On the Honda the ignition key is in the ON / RUN position. On a Chrysler vehicle you will need to engage the starter so the crankshaft is rotating and the ASD relay closes to provide power to the injector and coil.

At time interval 6:22 the presenter shows how to check for proper ground at the fuel injector harness. Again engage the starter and you should see pulsing on the test lamp. That means the PCM can control and ground the fuel injector electrical circuit. No pulsing means the PCM has failed.

Do a similar test on the 2 control wires between the coil and PCM. Test lamp should show pulsing on coil control wires.

 

[Lcattin]

Thank you. I will get a test light tomorrow. Looks like Harbor Freight sells them.

Just an FYI, if the computer is damaged there is a company in Illinois that tests and repairs them and sends them back for $115 and they supposedly give a lifetime warranty on the repair. I found them on Ebay and used them to fix a Durango ECM a while back.

 

[AllanC]

You are on the right track. Let's hope the PCM is not damaged but it is nice to know of a reliable and reasonably priced service if replacement is necessary.

 

[Lcattin]

Thanks again AllanC. Drove to the nearest Harbor Freight and got their computer safe LED test light and tested both the ignition and injector harness. Both had 12v but there was no life in the control circuits on either. I just unplugged one injector and the plug for the coil and tested them that way. Is that acceptable or do I have to leave them plugged in and back probe them?

 

[AllanC]

If you followed similar instructions in the video that checks for pulsing of the Honda on its fuel injector circuit (PT Cruiser engine in cranking mode) then you should be able to make the call that the PCM has failed. You could try and check for pulsing on each of the fuel injectors to get greater confirmation. You can reconnect 1 injector and back probe the control circuit pin but I expect you will get the same result, no pulsing.

After you replace the PCM I would return to the area of the wire harness that had several wires fused together. Tape the wires and make sure they are not suffering abrasion from a metal surface nor in contact with a hot surface (exhaust manifold, heater pipe, etc). You do not want the same problem to occur again.

 

[Lcattin]

Thanks for the reminder on the wires. I have begun that process but it has turned cold here so I will wait till we get some fair weather back again.

When I get the ECM back from repair and get the wiring checked out once again i will post the results here.

Thank you again for the guidance in this process.

 

[Lcattin]

Got a call from the repair facility that was working on my ECM and they said it was not repairable. The main cpu was damaged.

If I get a unit from my local salvage yard I know it will have to be programmed by a dealer but my question is will it even start or will the unit that reads the key security shut it down?

 

[AllanC]

. . . If I get a unit from my local salvage yard I know it will have to be programmed by a dealer but my question is will it even start or will the unit that reads the key security shut it down? . . .

The programming procedure for a replacement ECU will identify it properly to all nodes on the network. The sentry key works through the wireless module and it is one node on the network. A properly programmed ECU will communicate accordingly with the wireless key security. If you install the replacement ECU without programming the engine may not start or start and run briefly for 2 seconds and then die.

 

[valiant67]

Not every computer can be flashed for a new VIN. I would make sure any used one can be programmed by the dealer before purchase. If it were me, I'd skip the junkyard computer and get one from one of the reputable remanufacturers. They will load the proper software, program your VIN and set the proper mileage.

 

[Lcattin]

Thanks for that advice. I am looking on ebay right now.

 

[Lcattin]

Received a replacement ECM today. Installed and the car fired right up.
Thank you all for the help and advice.

Thanks to AllanC for leading me through the trouble shooting process. It was a great lesson.

It was good to hear it come to life.