P0128 caused by the temp sensor reading not being read by the PCM.

Question

Engine operates normally but check engine light is on and temp gauge shows no reading. A/C doesn't blow cold air. P0128 code is stored. Replaced temp sensor with no change in symptoms. Problem is intermittent meaning that sometimes the temp gauge shows a reading and the a/c works as it should and sometimes the temp gauge reading goes to 0 and the a/c then doesn't blow cold air, meaning the compressor clutch shuts off.

Answer 1

it sounds like u have a open to short in your wiring u need to check for power and ground at sensor wiggle wire harness around see if it goes off or statrs working like it should ..real common problems with gms.. harness get breaks in them or squrils rats love harness. .lol check for faulty relay..sometimes they will be intermittented ..most common is when car gets up to running tempand everythings running the relay might break down under the heat of engine bay ..

Comments

I wiggled harnesses going to the PCM and reseated the fuses and relays in the under hood fuse block. The large harness that runs horizontally from the drivers side of the front of the engine showed that it was rubbing on a screw on the front of the block. I'm not sure that it was worn through to any wires but it may have been. That is the only problem area I've found. Without a wiring diagram it is hard to determine the exact wire routing from the sensor to the PCM. It's working now but for how long I don't know.

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well hopefully its fixed for u ..it could have been grounding out on that screw and causing your hole problem. .if u need more help ..i check this site all day long ..good luck ...