Pinpoint Test I: The Air Compressor Is Inoperative

Vehicle Dynamic Suspension

Pinpoint Tests

Pinpoint Test I: The Air Compressor is Inoperative

Refer to Wiring Diagram Set 41, Vehicle Dynamic Suspension for schematic and connector information. Diagrams By Number

Normal Operation

When the Vehicle Dynamics Module (VDM) engages the air suspension relay, fused battery voltage is supplied from Battery Junction Box (BJB) fuse 112 (30A) to the relay along circuit 1053 (LB/PK), the voltage travels through the relay and to the air suspension compressor along circuit 538 (GY/RD). The compressor is provided a ground path along circuit 57 (BK).

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



PINPOINT TEST I: THE AIR COMPRESSOR IS INOPERATIVE

NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multi-meter probes.

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I1 CHECK THE AIR COMPRESSOR RELAY


- Ignition OFF.
- Disconnect: Air Suspension Relay.
- Carry out the relay component test.

- Does the relay pass the component test?

Yes
GO to I2.

No
INSTALL a new air suspension relay. REPEAT the self-test.

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I2 CHECK CIRCUIT 1053 (LB/PK) FOR VOLTAGE


- Ignition OFF.
- Disconnect: Air Suspension Relay .
- Measure the voltage between air suspension relay cavity 30, circuit 1053 (LB/PK), harness side and ground.




- Is the voltage greater than 10 volts?

Yes
GO to I3.

No
VERIFY BJB fuse 112 (30A) is OK. If OK, REPAIR circuit 1053 (LB/PK). If not OK, REFER to the Wiring Diagrams to identify the possible cause of the circuit short.
REPEAT the self-test.

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I3 CHECK CIRCUIT 538 (PK) FOR AN OPEN


- Disconnect: Air Compressor C1179.
- Measure the resistance between air suspension relay cavity 87, circuit 538 (GY/RD), harness side and air compressor C1179-2, circuit 538 (GY/RD), harness side.




- Is the resistance less than 5 ohms?

Yes
GO to I4.

No
REPAIR circuit 538 (GY/RD). REPEAT the self-test.

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I4 CHECK CIRCUIT 57 (BK) FOR AN OPEN


- Measure the resistance between air compressor C1179-1, circuit 57 (BK), harness side and ground.




- Is the resistance less than 5 ohms?

Yes
GO to I5.

No
REPAIR circuit 57 (BK). REPEAT the self-test.

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I5 CHECK CIRCUIT 538 (GY/RD) FOR VOLTAGE


- Connect: Air Suspension Relay.
- Ignition ON.
- Trigger the air compressor ON active command.
- Measure the voltage between air compressor C1179-2, circuit 538 (GY/RD), harness side and ground.




- Is the voltage greater than 10 volts?

Yes
INSTALL a new air compressor. REFER to Air Suspension Compressor Service and Repair. REPEAT the self-test.

No
REPAIR circuit 538 (GY/RD). REPEAT the self-test.

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