DTC 04

Part 1 Of 2:

Part 2 Of 2:

CIRCUIT DESCRIPTION
When the Automatic Level Control (ALC) 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.
2. Checks the condition of circuit X470.
4. Checks the condition of circuits B25 and B56.
6. Check for an open in the internal coil of the relay.