GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 HUMMER 🢒 2004 🢒 H2 🢒 DTC 🢒 DTC C0712

Circuit Description

The air suspension compressor motor is switched ON and OFF via an air suspension relay which is controlled by the air suspension module. The air suspension module provides a switched path to voltage whenever compressor activity is required. The air suspension module monitors the compressor motor relay circuity to determine if the voltage level agrees with the command state.

Conditions for Running the DTC

Ignition ON

Conditions for Setting the DTC

Air suspension module senses relay circuity voltage does not agree with command state.

Action Taken When the DTC Sets
    • Air suspension functionality is suspended.
    • SERVICE AIR SUSPENSION message is displayed.

Conditions for Clearing the DTC

The DTC will clear when the condition for setting the DTC is removed.

Diagnostic Aids

This DTC is set when the compressor relay circuitry is shorted to ground, voltage and open.

Test Description

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

  1. During the air suspension relay operation, listen for an audible click. Command the ON and the OFF states. Repeat the commands as necessary.

    2.

  2. Verifies that the air suspension module is providing voltage to the air suspension relay.

    3.

  3. Tests for an open in the ground circuit to the air suspension relay.

    4.

  4. Tests for constant voltage to the air suspension relay.

Step

Action

Yes

No

Schematic Reference: Suspension Controls Schematics

1

Did you perform the Air Suspension Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Air Suspension

2

Important: Be sure all doors are closed and engine is running for this test.

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine ON.
  3. With a scan tool, command the compressor relay ON and OFF.

Does the compressor relay turn ON and OFF with each command?

Go to Diagnostic Aids

Go to Step 3

3

Important: Be sure all doors are closed and engine is running for this test.

  1. Turn OFF the ignition.
  2. Disconnect the compressor relay.
  3. Turn ON the ignition, with the engine ON.
  4. Connect a test lamp to ground.
  5. Probe the control circuit of the compressor relay with a test lamp that is connected to ground.
  6. With a scan tool, command the compressor relay ON and OFF.

Does the test lamp turn ON and OFF with each command?

Go to Step 4

Go to Step 5

4

Important: Be sure all doors are closed and engine is running for this test.

  1. Connect a test lamp between the control circuit of the compressor relay and the ground circuit of the compressor relay.
  2. With a scan tool, command the compressor relay ON and OFF.

Does the test lamp turn ON and OFF with each command?

Go to Step 8

Go to Step 10

5

Does the test lamp remain illuminated with each command?

Go to Step 7

Go to Step 6

6

Test the control circuit of the compressor relay for a short to ground or an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

7

Test the control circuit of the compressor relay for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

8

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

Did you find and correct the condition?

Go to Step 13

Go to Step 11

9

Inspect for poor connections at the harness connector of the Air Suspension Module. Refer to Testing for Intermittent Conditions and Poor Connections and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

10

Repair the ground circuit of the air suspension relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the air suspension relay.

Did you complete the replacement?

Go to Step 13

--

12

Important: Always perform the check trim height procedure after air suspension module replacement.

  1. Replace the air suspension module. Refer to Module Assembly Electronic Suspension Control Replacement .
  2. Perform the trim height calibration procedure for the air suspension module, if necessary, after check trim height procedure.

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.

Does the DTC reset?

Go to Step 2

System OK