What is your question?
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What is your question?
The check engine light was not initially coming on at all when in Self test mode with the key in the ignition preventing me from getting a smog. I ran the diagnostic on the truck and it came out with P0650 code for the "Malfunction indicator control circuit." 1st: the truck runs great and only has around 68,000 miles on it. I popped off the dash and removed the entire unit and tested the bulbs to see if that would solve the issue simply, but all the bulbs tested positive for connection. 2nd: Took the truck to shop to have some wiring redone specific to the indicator lights for the dash as some were chewed by mice due to sitting. 3rd: The light came on but very DIM after I got the wiring done at the shop, but now it wont go off at all when the car has is in self test and/or running. 4: I have not quite gone the 70 or so miles yet but the light still has yet to turn off with no noticeable driving issues. (I took out the seat warmer fuse) not issue tho. 5: thinking it is CPU? thoughts?
How long has your 2002 GMC Sonoma had this problem?
June 2019
2 Replies
This one requires following shop manual procedures for testing step by step. Too much to try and coach here; obtain a shop manual or a resource like www.alldatadiy.com for this information. 1st - not a bulb issue 2nd - almost assuredly a wiring issue if you've had evidence of rodent activity. This makes total sense. 3rd - the light will not go off if there is still a problem present 4th - you cannot perform a drive cycle until the problem is resolved. 5th - no, I think it's a wiring concern. Processors are not normally the cause of most failures. In cases of weird codes, I always look for variables -- your rodent activity is the smoking gun here. You need to painstakingly check every wire related to this concern and ensure there is continuity and no resistance. Power where power belongs, ground where ground belongs. Good luck.
Pin out testing at ECM for proper ground driver circuit to CEL will be required - also testing for sufficient battery voltage supply circuit needs to be included.. Rodent damage presents one of the most difficult repair problems a technician will encounter.. I’ve witnessed ‘some’ vehicle that were actually damaged beyond reasonable repair from this same scenario. Good luck!
Additionally - the code will naturally be set if the ECM isn’t receiving the correct signal from the monitored circuit - wiring damage is the most likely suspect. I can’t recall the last time I had to replace a control module - failures certainly can happen but for the most part the control modules are very reliable - they are often mistakenly replaced.
Thank you; yeah I am thinking I'll have to take it by the dealership as the entire wiring may need to be redone for the instrument panel.. Odd that it is only effecting the check engine light and sometime the airbag light comes on and shuts off intermittently as well.
MICE is the suspect here - they love to make vehicles their playground or home. They’ve even been known to infest lawn tractor engines - restricting the air flow that cools these engines - overheating and exhaust valve seat failures are certain to occur.. Get some d-CON - traps or even a cat to eliminate these pest or this problem will certainly continue .. Otherwise mouse ‘proofing’ is simply not possible. Again - good luck!
Thank you for the response; the mice are killing me here! Probably going to have to replace the entire set of wires for instrument cluster.