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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15181
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I'm working on a 2001 Chevy suburban, replaced a compressor,

Customer Question

I'm working on a 2001 Chevy suburban, replaced a compressor, dryer, orifice tube, and also the climate control cluster. Still the compressor won't engage, checked all fuses, good. Checked at relay have power where it should be, but don't get ground, if I jump a ground wire in it works, any advice on what I can look for?
Submitted: 9 months ago.
Category: Chevy
Expert:  C. Walker, Jr. replied 9 months ago.

Have you replaced the low pressure switch?

Customer: replied 9 months ago.
Have not replaced it, but have tried jumping around it.
Expert:  C. Walker, Jr. replied 9 months ago.

That is where your ground comes from controlled by the pcm. If you jump ground from the low pressure switch will it run?

Customer: replied 9 months ago.
Tried jumping across the plug on lp switch, nothing. Tried going from each side separately straight to ground and still nothing.
Expert:  C. Walker, Jr. replied 9 months ago.

Okay disconnect the connector and jump to the black wire. If that does not work tell me what you are grounding to the compressor. It could be shorted at the splice before the compressor.

Customer: replied 9 months ago.
I'm not exactly understanding what you are wanting me to do, if I pull the relay out I can connect a ground to one of the posts and get the compressor to engage, wouldn't that eliminate the wiring by the compressor?
Expert:  C. Walker, Jr. replied 9 months ago.

If you disconnect the low pressure switch you should have no problem backprobing and bringing it to ground. The low side switch goes directly to a splice than to the compressor. Earlier you stated if you jumped ground it would work. SO this leaves the low pressure switch the pcm or the wires from the pcm low pressure switch to the compressor.

Customer: replied 9 months ago.
We have tried tracing everything out to no avail. During this process I found that there is not power to the obd2 port, do you think it is related?
Expert:  C. Walker, Jr. replied 9 months ago.

It should not effect the ac. Can you tell me what spot you jump to get it to engage.

Customer: replied 9 months ago.
If I go from one of the posts on the relay and jump in a ground wire, it will engage the compressor. I have also checked the wires going into the pcm, not sure which one it is exactly now, but I can apply voltage and also get to engage.
Expert:  C. Walker, Jr. replied 9 months ago.

Did you check the CIGAR fuse?

Customer: replied 9 months ago.
I did check it, replaced it, now have power at the obd2, but still won't connect to ecu, did not help ac at all, it has a check engine light on, but won't let me scan it
Expert:  C. Walker, Jr. replied 9 months ago.

Does the scan tool power up when you turn it on?

Customer: replied 9 months ago.
powers up, but says it can't connect to ecu
Expert:  C. Walker, Jr. replied 9 months ago.

I think you have a bad ecu to be honest. Starting to point that way to me. Did you jump 12v to the ecu?

Customer: replied 9 months ago.
Where would I jump it to? I was starting to think the same thing, if I get a used from a junk yard, does it have to be programmed?
Expert:  C. Walker, Jr. replied 9 months ago.

You said you jumped one of the wires that go to the ecu for the ac and it went on. Just wondering. But yeah if you get a used one that matches your vehicle options than no you will not need any programming.

Customer: replied 9 months ago.
if I remember it was wire 17, I applied 12v to it and the ac engages. Do you know if there are two ecu or pcms or is it just one piece?
Expert:  C. Walker, Jr. replied 9 months ago.

Just the one. All of the wires going to the AC should be a 5v ref voltage 12v would fry the ecu..

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