For 1990-2009 cars

### Circuit Description

When the automatic level control (ALC) sensor detects an out of trim condition, the rear suspension leveling air compressor relay K19 energizes in order to provide B+ to the rear suspension leveling air compressor. The automatic level control sensor continuously monitors the controlling circuitry in order to determine if B+ is present for a compress sequence or an air replenishment cycle (ARC).

### Conditions for Setting the DTC

The sensor detects that the relay output is not pulled down to ground when the sensor output is active.

### Action Taken When the DTC Sets

• | The LEVELING indicator lamp flashes.

• | The sensor's discrete low side output drive for the relay is disabled.

• | The sensor continuously attempts to recover from the fault.

### Conditions for Clearing the DTC

• | A current DTC becomes a history DTC when conditions for the fault are no longer present and the ignition cycles from OFF to ON.

• | A history DTC will clear after 20 ignition cycles.

• | Use a scan tool in order to clear this DTC.

### Diagnostic Aids

Inspect for the following conditions if a history or intermittent DTC is indicated:

• | A damaged wiring harness

| Inspect the wiring harness for damage. If the wiring harness appears to be in good condition, observe the display on the DMM while moving the connectors and wiring harnesses related to the circuits. A change in the DMM display during this test will indicate the location of the fault.

• | For additional information, refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

### Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. This step checks circuit B25 and circuit B56.

2. This step replaces the ALC sensor.

#### DTC 05 Compressor Relay Short to Battery

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Automatic Level Control (ALC) system Check performed | -- | Go to Step 2 | Go to Automatic Level Control Suspension System Check
2 |

1. Disconnect the rear suspension leveling air compressor relay K19 from the relay box.
2. Turn the ignition switch to the ON position.
3. Use a DMM in order to measure the voltage between terminal C of the ALC sensor connector and a known good ground.

Is the voltage equal to the specified value?

B+

Go to Step 3

Go to Step 4

3 | Locate and repair a short to B+ in circuit B25 and/or circuit B56. Is the repair complete? | -- | Go to Step 5 | --
4 | Replace the ALC sensor. Refer to Automatic Level Control Sensor Replacement . Is the replacement complete? | -- | Go to Step 5 | --
5 |

1. Clear any DTCs.
2. Connect all of the connectors that were disconnected.
3. Reinstall the components that were removed.
4. Wait at least 5 minutes.
5. Turn the ignition switch to the ON position.

Is the LEVELING indicator lamp flashing?

--

Go to Step 1

System OK