GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 GTO 🢒 DTC 🢒 DTC P1539

Circuit Description

The powertrain control module (PCM) activates the A/C clutch relay when the PCM detects that A/C has been requested. When activated, voltage should be present at both the A/C compressor clutch and the A/C compressor clutch supply voltage circuit at the PCM.

A DTC P1539 sets if the PCM detects voltage on the A/C compressor clutch supply voltage terminal when the system has not requested the A/C. A short to voltage at any point in the A/C compressor clutch supply voltage circuit, or the A/C relay contacts being stuck, also sets a DTC P1539, which is a type C DTC.

Conditions for Running the DTC
    • The ignition is turned ON.
    • A/C is not requested.

Conditions for Setting the DTC

The PCM detects voltage on the A/C compressor clutch supply voltage circuit for more than 15 seconds after the PCM has disengaged the A/C clutch relay.

Action Taken When the DTC Sets
    • The PCM will not illuminate the malfunction indicator lamp (MIL).
    • The PCM records the operating conditions at the time the diagnostic fails.
    • The PCM stores this information in the Failure Records.
    • The multifunction display (MFD) in the instrument cluster will display a message at key-on and key-off.

Conditions for Clearing the DTC
    • The DTC will become history if the PCM no longer detects a failure.
    • The history DTC will clear after 40 fault-free ignition cycles.
    • The DTC can be cleared with a scan tool.

Diagnostic Aids

The A/C compressor clutch supply voltage circuit goes to the A/C compressor clutch and to the PCM from the A/C clutch relay. Inspect all circuits going to these components.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Verifies the condition is present.

    2.

  2. Determines if the A/C compressor clutch relay is at fault.

    3.

  3. Determines if the PCM is at fault or the A/C compressor clutch supply voltage circuit is at fault.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2

Important: Diagnose P1546 first if it is set.

  1. Install a scan tool.
  2. Start the engine.
  3. Turn OFF the A/C and let the engine idle.
  4. Observe the A/C Request Signal and the A/C Relay Command parameters.

Does the A/C Request Signal display YES and the A/C Relay Command display ON when the A/C is not requested?

Go to HVAC Compressor Clutch Does Not Disengage

Go to Step 3

3

With a scan tool, observe the A/C Clutch Feedback Signal parameter.

Does the A/C Clutch Feedback Signal parameter display ON?

Go to Step 4

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

4

Remove the A/C compressor clutch relay.

Does the A/C Clutch Feedback Signal parameter display OFF?

Go to Step 6

Go to Step 5

5

Test the A/C compressor clutch supply voltage circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 7

6

Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement .

Did you complete the replacement?

Go to Step 8

--

7

Important: The replacement powertrain control module (PCM) must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls.

Did you complete the replacement?

Go to Step 8

--

8
  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

Go to Step 2

System OK