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Sweet35th
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Richard, I recently had the exact same concern on my wifes 2011 Cayenne S with 63k on it. Cylinder 8 misfire (P0308) and would come up with PSM failure, auto stop disabled, abs, 4wd system, etcetera. I found the spark plugs were original, and I had 4 cracked ignition coils. I replaced all spark plugs and the 4 cracked coils. This resolved both concerns. My suspicion is that RFI from the cracked coils is likely occurring, which can interfere with any Hrtz or Voltage signal from other sensors, and can simply ***** off multiple modules. I see this in the dealership all the time on other makes of vehicles (been a Ford senior master tech for 20 years now). Its generally hard to diagnose, but typically leads to ignition or charging system issues causing the RFI interference . Since you are throwing a misfire code (as was I), it is most likely that is the cause. I would repair the condition, clear all codes and recheck. My wife and I have since put on another 4000 miles with no issues. We are also replacing the remaining 4 coils as a precautionary measure. Replacing the plugs and coils is a very quick and easy task, with the only special tool needed is an inverted torx socket. The whole job should not take much more than an hour.