Thread: 2001 Pontiac A/C HELP!!

I have a tough problem here:

1) The "a/c" light comes on when you push the button on dash.
2) all relays and diode are OK. (swaped and used DVM).
3) The system is charged with feon.
4) If i jumper the clutch relay the clutch engages- so the clutch is OK.
5) There is NO (ZERO) 5 volt reference at the a/c pressure sensor.

This 5 volts comes from the PCM (grey wire) and the same voltage supplies the MAP sensor and the a/c evap temp sensor.

I would like to check to see if the 5 volts is present on the MAP and the Temp sensor but i don't know where they are. I need advice here. Also if there isn't 5 volts at all all 3 sensors that share this signal it might indicate a PCM problem. Where is the PCM on my car??--I looked behind glove box and in the air cleaner box? I would like to test the PCM for 5 volt output. Is there a good probe place? Is the PCM servicable? My next stop is the dealer if no one can help me. Thanks for reading my post.

I have 2001 GP also that had the same problem. Turns out that I had a broke wire going to the pressure switch, located on the driver side under the air intake next to the air cleaner box. The broke wire was on the main harness just at the end of the pigtail going to the pressure switch. I just spliced mine. The way I found out what the problem was is with a schematic tracing the wire from the ECM to the pressure switch and checked for resistance. Wasn't the easiest to get to but beats an exspensive trip to the garage.

Originally Posted by Bartbk02

I have a tough problem here:

1) The "a/c" light comes on when you push the button on dash.
2) all relays and diode are OK. (swaped and used DVM).
3) The system is charged with feon.
4) If i jumper the clutch relay the clutch engages- so the clutch is OK.
5) There is NO (ZERO) 5 volt reference at the a/c pressure sensor.

This 5 volts comes from the PCM (grey wire) and the same voltage supplies the MAP sensor and the a/c evap temp sensor.

I would like to check to see if the 5 volts is present on the MAP and the Temp sensor but i don't know where they are. I need advice here. Also if there isn't 5 volts at all all 3 sensors that share this signal it might indicate a PCM problem. Where is the PCM on my car??--I looked behind glove box and in the air cleaner box? I would like to test the PCM for 5 volt output. Is there a good probe place? Is the PCM servicable? My next stop is the dealer if no one can help me. Thanks for reading my post.