There is no power to the low-pressure switch

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

How do I test it coming from PCM?

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

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?

Dark green wire on the red connector.

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

Roy

What's the voltage and which of the three wires is the power supply to the low pressure switch?

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.