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Discussion Starter · #1 · (Edited)
I have a 2005 PT Cruiser 2.4 non turbo with approximately 74,000 miles on it.

I hired a mobile mechanic off Craigslist to come and evaluate my car In the end he determined that the P0129 and P0122 error codes were being caused not by faulty wires from the sensors, but the PCM itself giving out errors/failures. He used a multimeter to test the wires and he also tested for a spark.

This all started when about 2 months ago I got a camshaft sensor error and replaced to the camshaft sensor. It was the first major car work I'd ever done, and as a person who fixes computers I thought it was relatively simple. For two days the car did work but shortly after that it began to sputter and stopped running, breaking down in front of a Firestone.

I went back to the O'Reilly auto parts that sold me the camshaft sensor and they mentioned that it may just be a bad connector. I decided to detach the cable and blow compressed air into the connector and suddenly the camshaft sensor seemed to be working.

Weeks later or maybe a month or so (Now) I'm getting these p1022 and p1029 door codes.

I found that the errors can be: No spark, electrical wiring is bad, or the sensor is actually bad, or the PCM is bad.

My question is this mobile repairman off Craigslist is now telling me to purchase a $100 PCM off of eBay and stick it into the car. He wants to charge me $120 to do that.

Will there be any additional steps besides just screwing it into the car and plugging it in? I had a few other auto mechanic places tell me that they would need a specialist to reset or program the PCM?

I appreciate any advice you may have, if this is even the correct course of action I've been told, or not. Thanks in advance!
 

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I would consider the fact the parts place sensor may be junk.
If you’re purchasing a used computer, it will need reprogrammed for your VIN. Is the mobile repair person doing that?
 

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Welcome to Allpar. When confronted by multiple fault codes, I look at the 'Possible Causes' to see what they may share in common. It is unusual for more than one sensor to fail at a time. Note that both the TPS and Baro (MAP) share a 5 volt line (Or) from the PCM (S109 below).
The MAP sensor reads the barometric pressure (P0129) before the car is cranked and the TPS measures 'low' (P0122).
I would look very carefully at the 5 volt line. It would be wise to monitor it with a long wire and voltmeter while driving.
Rule out the external things before condemning the PCM. The PCM is at the bottom of the Possible Causes list for a reason. Everything else must be ruled out before suspecting the PCM.
Notice in the wiring diagram that the pot wipers (Bk/LB) are spliced together (S106) and tied to ground. One end the pot is to the 5 volt supply and the other end supplies the signal to the PCM.
Always diagnose first.


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Font Number Screenshot Parallel Document




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Discussion Starter · #4 ·
I would consider the fact the parts place sensor may be junk.
If you’re purchasing a used computer, it will need reprogrammed for your VIN. Is the mobile repair person doing that?

"Parts place sensor?" Is that a part I should look to buy and install to replace in my car?

I'm not familiar with it and a general Google search didn't bring anything up immediately.

Thanks.
 

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"Parts place sensor?" Is that a part I should look to buy and install to replace in my car?

I'm not familiar with it and a general Google search didn't bring anything up immediately.

Thanks.
I mean a cheap non-OEM sensor from a parts store. Either a Mopar brand sensor, or one from the OEM supplier, is often a higher quality part.
 

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You confused me with what may be a typo. You posted codes "P1022" and "P1029". But are they really "P0122" and "P0129"?
If so, and if you are getting two failed sensor codes, I would agree with IC, it's almost impossible that 2 sensors fail together. I'd suspect either a bad ground connection, or the 5V line, as he suggests. Either condition will corrupt the signals from these sensors, and they use the same 5V line and probably the same ground. Don't replace any sensors until you check the 5V and ground connections thoroughly.
 
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In addition to what Bob Lincoln and IC stated; the third party aftermarket cam position sensors are notoriously bad. I replaced one on my PT and ran fine for a few days and then the engine would misfire and sputter. It seemed very intermittent. I finally replaced it with a MOPAR sensor (from the dealer), and all went back to normal. I also had various error codes and they cleared when I replaced the sensor.

As stated above, don't jump at buying the PCM. If you do need one, there is a guy on here (myckee) that sells PCMs and has a great reputation.
 
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How tight did you tighten the bolts that hold the cam sensor? There's a magnet behind a plate where that sensor goes. If you over torqued the bolts, you MIGHT have cracked the magnet. I'd check that. I'm not sure what the torque spec is for those bolts, but it's in inch pounds, NOT foot pounds.
 

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Don't buy any sensors yet. You have to make sure that the wiring is good before investing in parts.
Always diagnose first.
 
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. . . Welcome to Allpar. When confronted by multiple fault codes, I look at the 'Possible Causes' to see what they may share in common. It is unusual for more than one sensor to fail at a time. Note that both the TPS and Baro (MAP) share a 5 volt line (Or) from the PCM (S109 below). . . . .

. . . . Notice in the wiring diagram that the pot wipers (Bk/LB) are spliced together (S106) and tied to ground. One end the pot is to the 5 volt supply and the other end supplies the signal to the PCM. . . . .
To add to the detail that contributor ImperialCrown has mentioned, there could be corrosion in splices S109 and S106. S106 provides 5 volt power to the sensors and S109 provides ground return path. Attached image shows location of S106 and S109.

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Discussion Starter · #13 ·
In addition to what Bob Lincoln and IC stated; the third party aftermarket cam position sensors are notoriously bad. I replaced one on my PT and ran fine for a few days and then the engine would misfire and sputter. It seemed very intermittent. I finally replaced it with a MOPAR sensor (from the dealer), and all went back to normal. I also had various error codes and they cleared when I replaced the sensor.

As stated above, don't jump at buying the PCM. If you do need one, there is a guy on here (myckee) that sells PCMs and has a great reputation.
So you think if I find a MOPAR Camshaft sensor and replace the one I bought from ORiley's that will fix the other error codes that aren't related to a camshaft sensor? P0122 and P0129 are the ones I'm getting.

This would prevent the car from turning over?

Thanks
 

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Discussion Starter · #14 ·
I have a 2005 PT Cruiser 2.4 non turbo with approximately 74,000 miles on it.

I hired a mobile mechanic off Craigslist to come and evaluate my car In the end he determined that the P0129 and P0122 error codes were being caused not by faulty wires from the sensors, but the PCM itself giving out errors/failures. He used a multimeter to test the wires and he also tested for a spark.

This all started when about 2 months ago I got a camshaft sensor error and replaced to the camshaft sensor. It was the first major car work I'd ever done, and as a person who fixes computers I thought it was relatively simple. For two days the car did work but shortly after that it began to sputter and stopped running, breaking down in front of a Firestone.

I went back to the O'Reilly auto parts that sold me the camshaft sensor and they mentioned that it may just be a bad connector. I decided to detach the cable and blow compressed air into the connector and suddenly the camshaft sensor seemed to be working.

Weeks later or maybe a month or so (Now) I'm getting these p1022 and p1029 door codes.

I found that the errors can be: No spark, electrical wiring is bad, or the sensor is actually bad, or the PCM is bad.

My question is this mobile repairman off Craigslist is now telling me to purchase a $100 PCM off of eBay and stick it into the car. He wants to charge me $120 to do that.

Will there be any additional steps besides just screwing it into the car and plugging it in? I had a few other auto mechanic places tell me that they would need a specialist to reset or program the PCM?

I appreciate any advice you may have, if this is even the correct course of action I've been told, or not. Thanks in advance!
"Theres no spark the car wont start without spark. The computer is not getting the 5 volt refrence from the coil thats where we are at rn." Says the guy from Craigslist.
 

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It doesn't turn over? As in, the starter doesn't crank? Because that's what that phrase means.
Cranking without starting is something different.
 

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Discussion Starter · #16 ·
Yes, we can hear it cranking. It just doesn't start.

"Theres no spark the car wont start without spark. The computer is not getting the 5 volt refrence from the coil thats where we are at rn." Says the guy from Craigslist who looked at it.
 

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So you think if I find a MOPAR Camshaft sensor and replace the one I bought from ORiley's that will fix the other error codes that aren't related to a camshaft sensor? P0122 and P0129 are the ones I'm getting.

This would prevent the car from turning over?

Thanks
First, I would investigate that K7 5V line that IC posted about in post #3 above. That supplies 5V to both of the sensors for these error codes. If the 5V is verified, than it is possible you do have a situation with multiple bad sensors. The P0129 code is one I've gotten when I forget to reconnect the pressure sensor (located in the air duct to the throttle body). However, with the P0129 code, the engine always ran for me, and I would assume it shouldn't stop the engine from running. The other code is associated with the throttle position sensor. I've had to replace the TPS before but the engine always ran. However, it is possible the TPS is bad as well. It is also possible that the cam position sensor you installed is bad; as that is not uncommon with aftermarket parts.

I would do the following:
1) Verify that the 5V line (K7) is actually supplying 5V as it is supposed to and the grounds are good. The post from AllanC also mentions the splices.
2) If the 5V and ground is verified, I make sure the wiring of the connector to the cam position sensor is good, and the insulation is not torn and no shorting is occurring. I had that happen once.
3) If that checks out, then I would consider replacing the TPS and the Cam position sensor and see if that makes a difference. I would hold off on the pressure sensor since that should not stop the engine from running.

The main point I am making, and I think the others are to, is to start checking things first and leave the PCM as the choice of last resort. The TPS and the Cam position sensor should cost a good bit less than $100, so if the wiring checks out, that is your best choice. Don't throw money at the PCM first. And, as I stated in my previous message, Myckee here on Allpar has a great reputation for PCMs and seems very honest; much better than some on Ebay.

Hope this helps.
 
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Discussion Starter · #18 ·
First, I would investigate that K7 5V line that IC posted about in post #3 above. That supplies 5V to both of the sensors for these error codes. If the 5V is verified, than it is possible you do have a situation with multiple bad sensors. The P0129 code is one I've gotten when I forget to reconnect the pressure sensor (located in the air duct to the throttle body). However, with the P0129 code, the engine always ran for me, and I would assume it shouldn't stop the engine from running. The other code is associated with the throttle position sensor. I've had to replace the TPS before but the engine always ran. However, it is possible the TPS is bad as well. It is also possible that the cam position sensor you installed is bad; as that is not uncommon with aftermarket parts.

I would do the following:
1) Verify that the 5V line (K7) is actually supplying 5V as it is supposed to and the grounds are good. The post from AllanC also mentions the splices.
2) If the 5V and ground is verified, I make sure the wiring of the connector to the cam position sensor is good, and the insulation is not torn and no shorting is occurring. I had that happen once.
3) If that checks out, then I would consider replacing the TPS and the Cam position sensor and see if that makes a difference. I would hold off on the pressure sensor since that should not stop the engine from running.

The main point I am making, and I think the others are to, is to start checking things first and leave the PCM as the choice of last resort. The TPS and the Cam position sensor should cost a good bit less than $100, so if the wiring checks out, that is your best choice. Don't throw money at the PCM first. And, as I stated in my previous message, Myckee here on Allpar has a great reputation for PCMs and seems very honest; much better than some on Ebay.

Hope this helps.
All of this is definitely helping, I appreciate everyone's input. That's honestly the reason that I posted was because he wants to replace the PCM and I wanted to make sure we weren't going to find out it was a different issue or solution altogether.

I may or may not have mentioned before that this technician from Craigslist went to a junkyard and picked up a TPS sensor. He replaced it and it originally had the proper voltage I think, but the voltage was slightly better now with the one from the junkyard. I still cranks but won't start.

He said today, "Theres no spark the car wont start without spark. The computer is not getting the 5 volt refrence from the coil thats where we are at rn."
 

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All of this is definitely helping, I appreciate everyone's input. That's honestly the reason that I posted was because he wants to replace the PCM and I wanted to make sure we weren't going to find out it was a different issue or solution altogether.

I may or may not have mentioned before that this technician from Craigslist went to a junkyard and picked up a TPS sensor. He replaced it and it originally had the proper voltage I think, but the voltage was slightly better now with the one from the junkyard. I still cranks but won't start.

He said today, "Theres no spark the car wont start without spark. The computer is not getting the 5 volt refrence from the coil thats where we are at rn."
Did he verify the 5V? Also, if I am recalling correctly, if the cam position sensor is bad, you will not be getting a spark.
 

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Discussion Starter · #20 ·
Did he verify the 5V? Also, if I am recalling correctly, if the cam position sensor is bad, you will not be getting a spark.
I will ask if he verified the 5 volts. I am open to replacing the camshaft sensor again, but I just assumed if the camshaft sensor was bad not only will the car not start, you would also get an error code for the camshaft sensor like I did in the first place?
 
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