P1545 - FAULT CODE - OBD2

P1545 Code failures by brands

P1545 BUICK, CADILLAC, CHEVROLET, GMC: A/C CLUTCH RELAY CONTROL CIRCUIT

Description of DTC code P1545

Ignition voltage is sent directly to the A/C compressor clutch relay. This relay is controlled by the Powertrain Control Module (PCM), which grounds its control circuit using an internal solid-state device, known as a driver.

The primary function of the conductor is to supply the ground for the component being controlled. Each conductor has a fault line, which is monitored directly by the PCM. When this controller commands the activation of a component, the controller circuit voltage must be close to 0 volts. By the time the PCM commands the control circuit to turn off a component, this voltage should be close to the battery voltage.

If the fault detection circuit finds a different voltage than expected on the output circuit controlling the A/C compressor clutch relay, a line status fault occurs, and this will cause the P1545 OBD2 diagnostic code to be set.

Symptoms of fault code P1545

On certain vehicles the Check Engine light illuminates.
The air conditioning compressor remains off.

Causes of OBD2 P1545

The reasons for the P1545 OBDII fault code are as follows:

The air conditioning clutch relay wiring may have been damaged.
The air conditioning clutch relay circuit may be shorted.
The A/C clutch relay may be faulty.

Possible solutions of the DTC code P1545

The steps to follow to correct the DTC P1545 OBD2 code are:

Consult the TSBs.
Using a scan tool, command the A/C relay by turning it on and off in the Engine Output Controls list. You should hear a click as you turn the relay on for each command sent to it. If not, check the condition of its wires and connectors. Repair as necessary.
Check the voltage and ground signal on the switch side of the A/C compressor clutch relay. If the results show that there is a short circuit, make repairs as necessary.
If no damage to the circuit connections is found, suspect a bad relay and replace it.