DTC 004

CIRCUIT DESCRIPTION
When the automatic level control 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 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.
^ Diagnostic Trouble Code (DTC) 04 is stored as a history code at the end of the ignition cycle.

CONDITIONS FOR CLEARING THE DTC
^ A current Diagnostic Trouble Code (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 Diagnostic Trouble Code (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.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
2. This step checks the condition of circuit X470.
4. This step checks the condition of circuit B25 and circuit B56.
6. This step checks for an open in the internal coil of the relay.