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Brought my PT Cruiser back from the dead

 
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  #1 (permalink)  
Old 24 Feb 2019, 09:04 pm
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Default Brought my PT Cruiser back from the dead

I had a interesting problem with my 05 PT Cruiser GT. It would always start the first try of the day, but it would only run for about 5 minutes before it would die and not start for the rest of the day. Due to it being the winter and pretty cold out I did not have much of a chance to troubleshoot my stalling issue over the last few months.

Basically the car would start every time, one time a day then run for anywhere from 3 to 10 minutes then die. It would not restart it until the next day. When the engine would stall my code reader would show P1187 if the PCM was read immediately after the car stalled. After trying to restart the car more codes would randomly show up. They were P0122, P0129, P0335, P0340, P0573. Not all of the codes would show up every time, but P0335 and P0340 always did. So I replaced the crankshaft sensor and camshaft sensors. This did not resolve my stalling issue. Since the P1187 was a code that always came up I decided to look at the MAP sensor voltages. The interesting thing was that there appeared to be 5 volts at the MAP sensor connector so I assumed the 5 volt excitation was OK. Since random codes appeared to be coming up I figured the PCM might be toast. So I bought a used PCM from Myckee who graciously offered that if it did not fix my problem he would take it back. It did not fix my problem and he took it back. Thanks, Myckee. If you need a PCM get it from him. After that I got the service manual and looked at the actual pin outs for the sensors and how the +5 volt excitation, power return and sensor outputs to PCM were distributed. So I took voltage measurements at the MAP and TPS sensors KOEO, KOER and after it stalled. I found that the +5 Volt excitation to both sensors was going to 0.5 Vdc after the car stalled. An oddity in my measurements was that there was a voltage higher than the 0.5 vdc to the PCM MAP and TPS sensors. The 0.5 Vdc is obviously an improper voltage and one that would make all sensor output voltages incorrect. The +5 volt excitation is distributed among 6 sensors. I already had changed the cam and crankshaft sensors, so I knew they were good and I also previously ran the car with the MAP and TPS sensors disconnected. That left only two sensors, the VSS and AC pressure sensor. Since the VSS was easy to reach I disconnected it while I monitored the +5v excitation. The voltage went from 0.5 Vdc to 4.98 Vdc, a good voltage. I then was able to start the car and it ran until I shut it off. It's amazing to me that an apparently shorted VSS sensor could cause the car to die and not start. Another interesting thing to note is that the PCM is supposed to open the ASD relay if it does not see a crankshaft signal, but in this case it kept the ASD relay closed even though there was no crankshaft signal.

Last edited by pdbrains; 24 Feb 2019 at 10:00 pm. Reason: tired of typing on my phone and finished editing on my computer.
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Old 25 Feb 2019, 08:34 am
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Default Re: Brought my PT Cruiser back from the dead

Mopar electronics. Who among us REALLY understands them? Glad to hear you got it figured out, though. Congratulations!
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Old 25 Feb 2019, 09:52 am
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Default Re: Brought my PT Cruiser back from the dead

Quote:
Originally Posted by pdbrains View Post
the PCM is supposed to open the ASD relay if it does not see a crankshaft signal, but in this case it kept the ASD relay closed even though there was no crankshaft signal.
Congratulations on figuring it out. Not acting as designed probably caused not by being simply shorted but a shorted to ground. A shorted to ground injector killed my Supreme the same way. Do you have any troubleshooting tips?

Note: Tough read without code or abbreviation explanations.
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Old 02 Mar 2019, 11:20 am
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Default Re: Brought my PT Cruiser back from the dead

PDBRAINS, that's some mighty fine work there youngin'.


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Old 02 Mar 2019, 04:03 pm
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Default Re: Brought my PT Cruiser back from the dead

I looked for the VSS on all of the major auto parts sellers web sites and no one has the sensor. It has been obsoleted by Chrysler and no one makes a replacement. It seems that the 5 speed GT's are fairly rare and some parts are just not available.
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Old 02 Mar 2019, 05:31 pm
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Cool Re: Brought my PT Cruiser back from the dead

Quote:
Originally Posted by pdbrains View Post
I looked for the VSS on all of the major auto parts sellers web sites and no one has the sensor. It has been obsoleted by Chrysler and no one makes a replacement. It seems that the 5 speed GT's are fairly rare and some parts are just not available.
gonna have to search the wrecking yards.... hopefully you can find a couple of usable ones.
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