Circuit Description
The vehicles rear leveling compressor motor is switched on and off via a compressor motor relay which is controlled by the suspension control module. The suspension control module provides a switched path to ground whenever compressor activity is required. The suspension control module continually monitors the compressor motor relay circuitry to determine if the voltage level agrees with the commanded state.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0655 Level Control Compressor Circuit
Conditions for Running the DTC
Whenever the compressor is activated.
Conditions for Setting the DTC
| • | Open in the control circuit of the compressor motor relay |
| • | Short to ground in the control circuit of the compressor motor relay |
| • | Short to battery in the control circuit of the compressor motor relay |
| • | Open in the ignition 3 voltage circuit of the compressor motor relay |
| • | Open IGN 3 fuse |
| • | A malfunctioning compressor motor relay |
Action Taken When the DTC Sets
| • | The compressor motor relay is disabled for the remainder of the ignition cycle. |
| • | Stores a DTC C0655 in the suspension control module memory |
Conditions for Clearing the DTC
| • | The suspension control module no longer detects a open, short to ground, or a short to battery in the control circuit of the compressor motor relay. |
| • | Using a scan tool |
| • | A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present. |
Diagnostic Aids
Important: A leak in the air tube between the rear shocks and compressor will cause excessive running of the compressor motor. After approximately 5 minutes of continuous running without a change in body-to-wheel height or system pressure, the suspension control module will command the compressor motor relay to the off state for the remainder of the ignition cycle.
The following conditions may cause a malfunction to occur in the compressor motor relay:
| • | A short to ground in the control circuit |
| • | An open in the control circuit |
| • | A short to battery in the control circuit |
| • | An open in the ignition 3 voltage circuit |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Command both the ON and OFF states. Repeat the commands as necessary.
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Tests the coil of the relay for continuity.
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Tests for voltage at the coil side of the compressor motor relay. The IGN 3 fuse supplies power to the coil side of the compressor motor relay.
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Verifies that the suspension control module is providing ground to the compressor motor relay.
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Tests if ground is constantly being applied to the compressor motor relay.
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Test for a short to voltage or an open in the control circuit of the compressor motor relay.
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The replacement suspension control module must be calibrated.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Automatic Level Control Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the compressor turn ON and OFF with each command? | -- | Go to Diagnostic Aids | Go to Step 3 | |
Does the resistance measure within the specified value? | 30-90 ohms | Go to Step 4 | Go to Step 12 | |
Does the test lamp illuminate? | -- | Go to Step 5 | Go to Step 11 | |
Does the test lamp turn ON and OFF with each command? | -- | Go to Step 9 | Go to Step 6 | |
Does the test lamp remain illuminated with each command? | -- | Go to Step 8 | Go to Step 7 | |
Test the control circuit of the compressor motor relay for a short to voltage and an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 | |
8 | Test the control circuit of the compressor motor relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 |
9 | Inspect for poor connections at the compressor motor 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 14 | Go to Step 12 |
10 | Inspect for poor connections at the harness connector of the suspension 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 14 | Go to Step 13 |
11 | Repair the coil side feed circuit of the compressor motor relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | -- |
12 | Replace the compressor motor relay. Did you complete the replacement? | -- | Go to Step 14 | -- |
Replace the suspension control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 14 | -- | |
14 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
