For 1990-2009 cars

### Circuit Description

When the automatic level control sensor detects an out of trim condition, the rear suspension leveling air compressor relay K19 energizes to provide B+ to the rear suspension leveling air compressor. The automatic level control sensor continuously monitors the controlling circuitry to determine if there is B+ 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 up to B+ when the sensor output is deactivated and the ignition signal is active.

### Action Taken When the DTC Sets

• | The sensor flashes the LEVELING indicator lamp.

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

• | The compressor is inoperative.

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

• | DTC 04 is stored as a history code at the end of the ignition cycle.

### Conditions for Clearing the DTC

• | The DTC will clear when B+ is present at the low side output drive.

• | Using a scan tool.

### Diagnostic Aids

Refer to the diagnostic table.

### Test Description

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

1. Checks the condition of circuit X470.

2. Checks the condition of circuits B25 and B56.

3. Check for an open in the internal coil of the relay.

#### DTC 04 Compressor Relay Short to Ground/Open Circuit

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Has the Automatic Level Control (ALC) System Check been performed? | -- | Go to Step 2 | Go to ALC Suspension System Check .
2 |

1. Disconnect the rear suspension leveling air compressor relay K19 form the relay box.
2. Turn the ignition switch to the ON position.
3. Use a DMM to measure the voltage between terminal 3 at the relay box terminal 3 and a good known ground.

Is the measured voltage within the specified value?

B+

Go to Step 4

Go to Step 3

3 |

1. Locate an open, high resistance or short to ground in circuit X470.
2. Repair the open, high resistance or short to ground in circuit X470.

Is the repair complete?

--

Go to Step 9

--

4 |

1. Disconnect the ALC sensor connector.
2. Connect a fused jumper wire between terminal 3 and terminal 1 at the relay box.
3. Use the DMM to measure the voltage between terminal C of the ALC sensor connector and a known good ground.

Is the measured voltage within the specified value?

B+

Go to Step 6

Go to Step 5

5 |

1. Locate an open, high resistance or short to ground in circuits B25 and/or B56.
2. Repair the open, high resistance or short to ground in circuits B25 and/or B56.

Is the repair complete?

--

Go to Step 9

--

6 | Measure the resistance between terminal 3 and terminal 1 of the rear suspension leveling air compressor relay K19. Is the measured resistance within the specified value? | 45 ohms ohms-49 | Go to Step 8 | Go to Step 7
7 | Replace the rear suspension leveling air compressor relay K19. Is the replacement complete? | -- | Go to Step 9 | --
8 | Replace the ALC sensor. Refer to Automatic Level Control System. Is the replacement complete? | -- | Go to Step 9 | --
9 |

1. Clear any DTC.
2. Connect all of the connectors that were disconnected.
3. Reinstall all of the components that were removed.
4. Wait for 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