GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Corvette 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 DTC P1546

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 not detected when A/C is requested this DTC sets.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC
    • The PCM detects that A/C has been requested.
    • The PCM commands the A/C compressor clutch driver.
    • The PCM does not detect a voltage on the A/C compressor clutch supply voltage circuit that supplies voltage to the A/C compressor clutch.
    • 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 that battery voltage is supplied to the A/C compressor clutch relay.

    2.

  2. Tests if the A/C relay is at fault or the A/C compressor clutch supply voltage circuit is at fault.

    3.

  3. If the A/C clutch feedback signal parameter displays OFF, this indicates the PCM does not recognize voltage from the A/C compressor clutch supply voltage circuit.

    4.

  4. Tests for a high resistance or an open.

    5.

  5. 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 ON the A/C and let the engine idle for 5 minutes.
  4. 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 when the A/C clutch is engaged?

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

Go to Step 3

3

Important: For underhood electrical center relay terminal identification refer to Electrical Center Identification Views in Wiring Systems.

  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay from the electrical center 2.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition 1 voltage circuit at the A/C compressor relay terminal with the test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 9

4

Install a 10-amp fused Jumper wire between the ignition 1 voltage circuit to the A/C compressor clutch supply voltage circuit.

Does the A/C compressor clutch engage?

Go to Step 5

Go to Step 10

5

Important: The fused jumper wire should still be installed with the ignition on.

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

Does the scan tool indicate that the A/C Clutch Feedback Signal parameter is ON?

Go to Step 7

Go to Step 6

6

Test the A/C compressor clutch supply voltage circuit for a high resistance or an open. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 8

7

Inspect for poor connections at the A/C compressor relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

8

Inspect for poor connections at the harness connector of the powertrain control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

9

Repair the ignition 1 voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

10

Repair the A/C compressor clutch supply voltage circuit between the A/C compressor clutch relay and the A/C compressor clutch. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the A/C compressor clutch relay.

Did you complete the replacement?

Go to Step 13

--

12

Important: Perform the programming 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 13

--

13
  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