Open circuit or high resistance in the A/C clutch feed or feedback wiring; Corroded or loose connector at the compressor clutch or relay; Faulty A/C clutch relay or relay socket; Blown A/C clutch fuse; Open or shorted compressor clutch coil; Low refrigerant or a pressure switch holding the circuit open, so the clutch is never supplied; Faulty engine control module.

P1546

Air Conditioning (A/C) Clutch Feedback Circuit Low Voltage.

GMC
Powertrain
Manufacturer code
Low severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
5: AreaVehicle speed, idle control and auxiliary inputs
46: FaultThe specific fault in that area

What it means

P1546 on a GMC means the engine control module has detected low voltage on the air conditioning clutch feedback circuit. The module monitors the voltage at the A/C compressor clutch circuit and compares it with what it expects when it commands the clutch on or off. If the feedback reads low when it should be high, the code is set.

Symptoms

A/C blows warm or does not cool
A/C compressor clutch does not engage
Intermittent A/C operation
Check engine light on
Slight idle change or no idle compensation when A/C is requested

Possible causes

Open circuit or high resistance in the A/C clutch feed or feedback wiringlikely
Corroded or loose connector at the compressor clutch or relaylikely
Faulty A/C clutch relay or relay socketlikely
Blown A/C clutch fusepossible
Open or shorted compressor clutch coilpossible
Low refrigerant or a pressure switch holding the circuit open, so the clutch is never suppliedpossible
Faulty engine control modulerare

How to diagnose

Read the stored codes and freeze frame data, noting whether A/C was requested and the conditions when the code set
Check the A/C clutch fuse and relay, and inspect the relay socket for heat damage or corrosion
Inspect the wiring and connectors at the compressor clutch and along the harness for chafing, damage and corrosion
With A/C requested, check whether the clutch relay clicks and whether the clutch engages
Measure the voltage at the clutch connector with A/C on, and check the supply and ground
Test the clutch coil resistance against the specification for the model and engine
Check refrigerant pressure and the pressure switch inputs, as the wiring layout and switch location vary by model
Check the feedback wire for continuity back to the control module, following the wiring diagram for the vehicle

How to fix

Replace the blown fuse after finding and correcting the cause of the overload
Replace a faulty A/C clutch relay or damaged relay socket
Repair or replace damaged wiring and clean or replace corroded connectors
Replace the compressor clutch or coil if its resistance is out of specification
Correct low refrigerant by finding and repairing the leak, then recharge the system correctly
Replace or reprogram the control module only after all wiring and component faults are ruled out and a fault is confirmed

Can I keep driving?

Low severity

The car can normally be driven as the fault affects only the air conditioning and related idle compensation. Book it in at your convenience, and avoid using the A/C until it has been checked.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.