Pinpoint Test G: The Air Compressor Runs Continuously With The Ignition Switch in The OFF Position and No DTC Is Set

Vehicle Dynamic Suspension

Pinpoint Tests

Pinpoint Test G: The Air Compressor Runs Continuously With the Ignition Switch in the OFF Position and No DTC is Set

Normal Operation

With the air suspension system activated and the ignition switch in the ON position, the Vehicle Dynamics Module (VDM) uses input from the 2 suspension height sensors to determine if vehicle payload has changed enough to warrant the adjustment of the rear suspension. If an adjustment is necessary, the VDM will open the air spring solenoids and activate the air compressor to inflate the air springs and raise the rear suspension. To deflate the air springs and lower the rear suspension, the VDM will open the air spring solenoids and activate the vent solenoid.

With the air suspension system deactivated and the ignition switch in the OFF position, the VDM will ignore height sensor input and not adjust the rear suspension. When only the ignition switch is placed in the OFF position, the VDM will remain powered for approximately 40 minutes to allow the system to adjust the rear suspension due to changes in vehicle payload. The system can deflate (vent) at any time during these 40 minutes and will only inflate (pump) once during the last 30 seconds, if necessary. Once the 40 minutes has elapsed, the VDM will depower and ignore any height sensor input until the ignition switch is placed in the ON position.

To activate the air compressor, the VDM supplies voltage to the air compressor relay along circuit CCL01 (WH/VT). This voltage passes through the coil side of the relay and to ground along circuit GD123 (BK/GY), which energizes the relay. The switch side of the relay receives fused battery voltage from Battery Junction Box (BJB) fuse 19 (60A) along circuit SBB19 (BU/RD). When the relay is energized, the switch side closes and this fused battery voltage is sent to the air compressor along circuit CCL08 (BU/BN). The voltage passes through the air compressor and to ground along circuit GD123 (BK/GY), which activates the air compressor.

This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Air compressor relay
- VDM

PINPOINT TEST G: THE AIR COMPRESSOR RUNS CONTINUOUSLY WITH THE IGNITION SWITCH IN THE OFF POSITION

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G1 CHECK THE RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE


- Disable the air suspension system. Refer to Air Suspension System Disable/Enable Air Suspension System Disable/Enable.
- Ignition OFF.
- Disconnect: VDM C2131a.
- Remove the air compressor relay.
- Ignition ON.
- Measure the voltage between air compressor relay, circuit CCL01 (WH/VT), harness side and ground.




- Is any voltage present?

Yes
REPAIR circuit CCL01 (WH/VT). CLEAR the DTCs. REPEAT the self-test.

No
GO to G2.

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G2 CHECK FOR MODULE ACTIVITY


NOTE: If the key has been off for 39 minutes and 39 seconds, the compressor is permitted to run once for a maximum of 30 seconds.

- Ignition OFF.
- Connect: VDM C2131a.
- Connect: Air Compressor Relay.
- Enable the air suspension. Refer to Air Suspension System Disable/Enable Air Suspension System Disable/Enable.
- Ignition ON.
- Ignition OFF.
- Verify the air compressor still cycles for a maximum of 30 seconds after the ignition is turned OFF.
- Does the air compressor still cycle for greater than 30 seconds after the ignition is turned OFF?

Yes
GO to G3.

No
The system is OK. INFORM the owner of system operations.

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G3 CHECK THE VDM


- Disable the air suspension system. Refer to Air Suspension System Disable/Enable Air Suspension System Disable/Enable.
- Disconnect: VDM C2131a.
- Disconnect: VDM C2131b.
- Does the air compressor still cycle?

Yes
GO to G4.

No
INSTALL a new VDM. REFER to Vehicle Dynamics Module (VDM) Service and Repair. REPEAT the self-test.

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G4 CHECK CIRCUIT CCL08 (BU/BN) FOR A SHORT TO VOLTAGE


- Disconnect: Air Compressor Relay.
- Does the air compressor still cycle?

Yes
REPAIR circuit CCL08 (BU/BN). TEST the system for normal operation.

No
INSTALL a new air compressor relay. TEST the system for normal operation.

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