Functional Test Description

CAUTION: Functional test is run only if diagnosis does not identify concern. Excessive use of the functional test could overheat the compressor or damage system electronics.

DESCRIPTION
Functional tests are run at the end of the Auto/Manual test procedure, and are used as an aid to diagnose the system. The only way to enter the Functional Test is by first running the Auto/Manual test. During the Functional Test the control module will attempt to cycle the components as follows:

DTC 23:
Vent Rear-During this test the control module will attempt to open the vent solenoid valve and air spring solenoid valves as long as the Star tester button is pressed. The rear of the vehicle will lower.

DTC 26:
Compress Rear-During this test the control module will attempt to energize the air compressor and open the spring solenoid valves as long as the Star tester button is pressed. The rear of the vehicle will rise.

NOTE: DTC 26 is normally used to inflate the rear spring after installation.

DTC 31:
Air Compressor Relay Toggle-During this test, the control module will attempt to cycle the compressor relay ON for one second and OFF for one second repeatedly. This cycle will repeat for as long as the Star tester button is pressed. The compressor will be heard cycling ON and OFF if this test is successful.

NOTE: The extended use of this test can cause the self-resetting circuit breaker in the compressor to open. If this happens, allow the compressor to cool down for 15 minutes. Then, restart the diagnostic procedures.

DTC 32:
Vent Solenoid Toggle-During this test, the vent solenoid valve is opened for one second, then closed for one second. This cycle will repeat for as long as the Star tester button is pressed. The vent solenoid valve in the air compressor will be heard cycling ON and OFF if this test is successful.

DTC 33:
Air Spring Solenoid Toggle-During this test, both air spring solenoid valves will be opened for one second, then closed for one second repeatedly. This cycle will repeat for as long as the Star tester button is pressed. The control module cannot turn one spring solenoid valve on without turning the other solenoid valve on (Circuits 114 (BR/PK) and 115 (T/W) are tied together inside the control module). To verify that both solenoid valves operate, raise the vehicle on a hoist. Do not turn the air suspension switch OFF. Remain in Functional Test DTC 33. Then, touch each solenoid valve to verify that it is cycling ON and OFF.