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Electrical issues when hot or humid

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I've been having sporadic electrical issues with my 2006 997 for some time now. In certain situations, usually when it's hot or humid out (and sometimes when hitting a hard bump), I experience a PSM failure and a  Spoiler Failure. Recently the speedometer (both digital and analog) will also read 0mph while driving after this fault. 


I've pulled the fault codes with a Durametric (see below) and it seems to point to a faulty control module. When I took it to the dealer a while back, they also indicated it was a faulty ABS control unit.  However, what's suspicious to me is that it only happens in certain conditions, again, when it's hot or humid out or when hitting a hard bump.


The easy thing to do is to check the fault and say, "yep you need to replace that," but I'm curious if perhaps the problem could be more nuanced than that. Could it be a wiring issue somewhere in the car that, when it gets hot, the electrical resistance increases and the fault shows itself (similar to the issue with the starter wiring harness that was recalled)?  


I'm hesitant to just say go replace this part because it's quite pricey, only happens in certain situations, and most importantly, if the issue is elsewhere, I'd rather it be diagnosed properly and fixed.  Unfortunately these days people seem to jump right to replace rather than really diagnose and fix the issue.


Anyways, any help or advice would be appreciated.


Thanks in advance,






4223 - Fault in DMW - read out fault memory
C150 - Control unit communication engine electronics (drive)
C153 - Communication steering wheel electronics control unit (drive)
C101 - Control module faulty
C140 - Communication instrument cluster (display)
C158 - Communication gateway control unit (CAN drive)
C127 - Communication front control unit (comfort)
C152 - Communication PSM control unit (drive)
8036 - Right seat heater
8035 - Left seat heater
C152 - Communication PSM control unit (drive)
C202 - Fault PSM control unit (display)
C127 - Communication front control unit (comfort)
8035 - Interior sensor fan
C152 - Communication PSM control unit (drive)
8042 - Front luggage compartment unlocking
C152 - Communication PSM control unit (drive)
C202 - Fault PSM control unit (display)
8056 - Wheel speed/travel signal not OK
C127 - Communication front control unit (comfort)
C130 - Communication steering wheel electronics (comfort)
C152 - Communication PSM control unit (drive)


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Sorry for your issues. Sounds like a loose connection but other than that I unfortunately cannot offer anything diffinitive. I'll e following with interest as I have an '06 2CS.

Hope that others will chime in who may have a better idea.

Good luck.


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  • 3 months later...

I am having a similar problem with the Handbrake light in my instrument cluster. I posted this a month ago on Rennlist:


Over the past few days, while driving, the "HANDBRAKE!" warning light has been appearing in the instrument cluster. It will sometimes flash on and off within a second and other times it will stay on for a minute or two. Its also seems sensitive to road conditions so it will flash on after going over a bump. Also my handbrake in the 'off' position is very loose and is only laying flat because of gravity. It will jostle up and down a bit if going over a bumpy surface. 

This definitely seems like an electrical issue and not a physical issue with the brake shoes. It has been extremely hot and humid on Long Island lately so maybe there is a connection....


I've replaced the handbrake switch twice and that originally solved the problem but now the warning light is on constantly instead of blinking on and off. I think I've got a fray or bad connection on the yellow wire that goes from the handbrake switch to the PSM module. I removed all the plastic bits in the frunk and got access to the PSM but the loom and connector are too daunting.


Lastly, I drove the car to the market this evening and the handbrake light began blinking on and off...its been cooler and less humid....

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