GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The compress accumulator will detect conditions of excessive rear suspension leveling air compressor activity. This condition is usually due to the presence of pneumatic leaks or vehicle overload conditions. An accumulator timer will keep track of the accumulated run time of the compressor. The timer resets at each ignition cycle, or if an exhaust sequence has occurred.

Conditions for Setting the DTC

When the compressor is active for more than 3 minutes before the rear of the vehicle reaches a trim position.

Action Taken When the DTC Sets

    • All compressor intake activity is disabled.
    • The LEVELING indicator lamp flashes.

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

Refer to Automatic Level Control System Operation Check .