P1538

Steps 1 - 4:

Steps 4 - 10:

Steps 11 - 15:

DTC P1537 or P1538

Circuit Description
The air conditioning (A/C) compressor relay is controlled by the engine control module (ECM). The ECM controls the relay by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the ECM. When the ECM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, a DTC sets.

DTC Descriptor
This diagnostic procedure supports the following DTCs:
DTC P1537 Air Conditioning (A/C) Clutch Relay Control Circuit High Voltage
DTC P1538 Air Conditioning (A/C) Clutch Relay Control Circuit Low Voltage

Conditions for Running the DTC
The engine is running.
The ignition 1 voltage is more than 11.0 volts.
The A/C is requested ON.
The A/C compressor is running (P1537 only)
The DTC runs continuously once the above conditions are met.

Conditions for Setting the DTC
The ECM detects a low voltage on the A/C clutch relay control circuit for more than 25 seconds.
OR
The ECM detects a high voltage on the A/C clutch relay control circuit for more than 25 seconds.

Action Taken When the DTC Sets
The malfunction indicator lamp (MIL) will not illuminate.
The ECM will store conditions which were present when the DTC was set as Failure Records data only.
This information will not be stored in the Freeze Frame data.

Conditions for Clearing the MIL/DTC
DTCs can be cleared by using the scan tool.
Disconnect the ECM battery feed for more than 10 seconds.

Diagnostic Aids
For HVAC system concerns, refer to HVAC Preliminary Checks. - Preliminary Checks

If condition is intermittent refer to Diagnostic Aids.



A/C Clutch Relay Terminal Identification

B+ - Switch Ignition 1 Voltage - Coil
Control A/C Compressor Clutch


Listen for a click when the A/C compressor relay operates. When the relay is commanded On with the scan tool, the ECM pulses the relay ON and OFF several times. Repeat the command as necessary.