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Doug 4/20/2010

1997 GMC C1500 Sierra SL 6 Cyl 4.3L


Dash and motor gone bonkers

I have a GMC C1500 with 225262 miles on it . I hit a pothole and the check engine light came on and my dash gauges stoped working. Only thing that works on the das is tech,speedo is off by 5mph and trip odemitor. Fuel,volt,oil pressure and temp guage not working. When the truck is running it runs smooth then like s switch is thrown it runs rough, and loss of power when i floor it it hesatates and then black smooke out the pipe. I have changed the MAF,MAP and TBI throttle sensor like the compuer said. cleared the codes and the MAF to high and to low threshold readings came back again. Cleared the computer again and same thing again. Will run smooth and then like a switch thrown runs rough and hesatates up hills and all of sudden runs smooth again. any idea?

1 Answer


HouseCallAuto 4/20/2010

The very first thing that MUST be done is to attach a code reader (you will have to borrow or buy one - under $100) and read the fault codes stored in the computer memory. That is the way things are diagnosed. If there is no communication with the code reader then it may be a bad PCM.


Doug 4/23/2010

I used a code reader and cleared the codes from the computer and they came back again. I did find that the wiring harness had come in contact with the left vavl cover and had melted some and some wiring was damaged. Repaired the wiring and the dash gauges work half way but now i have to have them reclabrated to be correct.

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