P0031 and P0037 - Indication of a bad PCM?

[cromagnondan]

I'm new to the Turbo PT scene, but not new to PT's. I've recently acquired a 2005 PT Cruiser Touring Turbo Convertible. It has the following symptoms. After disconnecting the battery, no codes are present until the car reaches normal operating temperature, at which time the P0031 and P0037 appear. It affects performance by making the car stumble and hestitate on acceleration, cut out for a second as if the fuel were cut off and then cut back in which may also cause a backfire in the throttle body. It makes driving it a nerve-racking experience as it feels like it is just about ready to leave you stranded. I have read nearly every P0031 and P0037 post on ptcruiserlinks.com and can report that most owners who have received this problem have ultimately resolved it by replacing the PCM. Most people go down the route of replacing both 02 sensors, checking the wiring to the sensors, and then finally replacing the PCM, sometimes replacing it with many "rebuilt" units until a "good" one is found. Has anyone fixed a P0031, P0037 in a turbo by some means other than replacing the PCM? It seems that the 02 sensors are NEVER the reason for these codes, that the problem is there is no longer any output voltage from the PCM to the 02 heater circuit. Am I reaching the right conclusion? Is the only way to fix P0031 and P0037 to buy a new PCM?

[rob302]

it could be a faulty o2 ground as well. best to check with a multimeter before coughing up the dough for any parts

[NitroPT]

Welcome to the forum

[cromagnondan]

Well, after much consternation, I ordered the PCM from All Computer Resources. Only two days of use, but I can report the codes of P0031 and P0037 are gone. The idle is smoother, the slightly pulsing headlights (voltage regulator or uneven idle) are also gone. By the way, if you go looking for the voltage regulator, you will find that it, too, is part of the PCM, like the power supply for the oxygen sensors. ACR's PCM comes with a lifetime warranty, whereas the competitors offer a 1 year warranty. The difference was about $100, so it was worth it in my opinion. Now here is a interesting finding while Googling. Jeeps have 4 oxygen sensors, and Jeep owners report suddenly getting codes on all 4 oxygen sensors. The fix? A new PCM. (Its not just Chrysler, other manufacturers have gone the PCM route, with similar complaints.) No sure why the 2005 Turbo PCM is 300-800, but the 2005 NA is 200, but there are no other options. Driveability is dramatically improved. I no longer feel like each trip may end in a tow home. The symptoms when the codes were present were hesitation and stumbling until 40 mph, dead spots in acceleration ,backfiring in throttle body, and occasional shutdown (AutoShutDown relay?), etc. So, if you get the codes, I'd say a PCM is in your future.

[NitroPT]

Glad that your PT Cruiser is up and running again.
Thank you for coming back and reporting.

However I would not recommend others that get the same DTCs as you to just swap out a PCM. It is NOT that simple!

[myckee]

Originally Posted by cromagnondan

Well, after much consternation, I ordered the PCM from All Computer Resources. Only two days of use, but I can report the codes of P0031 and P0037 are gone. The idle is smoother, the slightly pulsing headlights (voltage regulator or uneven idle) are also gone. By the way, if you go looking for the voltage regulator, you will find that it, too, is part of the PCM, like the power supply for the oxygen sensors. ACR's PCM comes with a lifetime warranty, whereas the competitors offer a 1 year warranty. The difference was about $100, so it was worth it in my opinion. Now here is a interesting finding while Googling. Jeeps have 4 oxygen sensors, and Jeep owners report suddenly getting codes on all 4 oxygen sensors. The fix? A new PCM. (Its not just Chrysler, other manufacturers have gone the PCM route, with similar complaints.) No sure why the 2005 Turbo PCM is 300-800, but the 2005 NA is 200, but there are no other options. Driveability is dramatically improved. I no longer feel like each trip may end in a tow home. The symptoms when the codes were present were hesitation and stumbling until 40 mph, dead spots in acceleration ,backfiring in throttle body, and occasional shutdown (AutoShutDown relay?), etc. So, if you get the codes, I'd say a PCM is in your future.

Thanks for reporting back your efforts and results. While I wouldn't say that if anyone gets two oxygen sensor codes, that the fix is automatically a new/replacement PCM, I will say that I have encountered this phenomenon three times, and the fix, in all three cases, after normal diagnostic procedures, was to replace the PCM.

[NitroPT]