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There is no power to the low-pressure switch

Tiny
MIKEWOLFREY
  • MEMBER
  • 2002 CHEVROLET SILVERADO
  • 6.0L
  • V8
  • 4WD
  • AUTOMATIC
  • 350,000 MILES
The A/C control module is good and lights up like it should.
Friday, May 20th, 2022 AT 5:52 PM

7 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good evening,

The power for the low-pressure switch comes from the engine ECM. I attached a wiring diagram for you to view.

You need to test the wire from the ECM to the low-pressure switch.

Roy
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Friday, May 20th, 2022 AT 6:37 PM
Tiny
MIKEWOLFREY
  • MEMBER
  • 3 POSTS
How do I test it coming from PCM?
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Friday, May 20th, 2022 AT 7:52 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You need a test light or voltmeter.

I attached the pin you need to test for power.

If you have no power, the ECM is bad.

If you have power, you have a broken wire from the ECM to the low-pressure switch.

Roy
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Friday, May 20th, 2022 AT 8:08 PM
Tiny
MIKEWOLFREY
  • MEMBER
  • 3 POSTS
Is it the red or blue side? And do you unplug it to test the pin, or do you have to take the cover off the plug and test it from where the wire comes in?
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Sunday, May 22nd, 2022 AT 10:03 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Dark green wire on the red connector.

You can just back probe the connector and test for power.

Roy
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Sunday, May 22nd, 2022 AT 2:05 PM
Tiny
ROY JR MARTINEZ
  • MEMBER
  • 3 POSTS
What's the voltage and which of the three wires is the power supply to the low pressure switch?
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Saturday, April 29th, 2023 AT 6:04 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,513 POSTS
The low-pressure switch has no power and only two wires. It connects the ground circuit and signals the PCM here is the complete AC wiring diagrams so you can see how the system works. Check out the images (below). Please let us know what you find.
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Sunday, April 30th, 2023 AT 10:34 AM

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