GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Corvette 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC P1539

Circuit Description

The PCM will activate the A/C clutch relay when the PCM detects that A/C has been requested. When the PCM activates the relay, voltage should be present at both the A/C compressor clutch and the A/C compressor clutch supply voltage circuit at the PCM. If voltage is detected when A/C is not requested this DTC sets.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC
    • The PCM detects a voltage on the A/C compressor clutch supply voltage circuit when the A/C is not requested.
    • The condition is present for at least 20 seconds.

Action Taken When the DTC Sets
    • The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
    • The PCM stores the failure records.
    • The A/C compressor clutch is disabled.

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.

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.

    4.

  4. Perform the recalibration procedure for the powertrain control module.

Step

Action

Yes

No

Schematic Reference: HVAC Schematics

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

Important: Diagnose P0645 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. With a scan tool, observe the A/C Request Signal and the A/C Relay Command parameters in the Powertrain, Engine Data 2 list.

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 Engage or HVAC Compressor Clutch Does Not Disengage

Go to Step 3

3

With a scan tool, observe the A/C Clutch Feedback Signal parameter in the Powertrain, Engine Data 2 list.

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.

Did you complete the replacement?

Go to Step 8

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7

Important: Perform the recalibration procedure for the powertrain control module .

Replace the powertrain control module. 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 as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK