Retrieving and Clearing DTCs

Diagnostic Instructions
The control module has the capability of performing either a series of diagnostic tests on the air suspension system or to fill the front and/or rear air springs. Specific instructions for using the air fill capability are under Air Spring, Service and Repair, Refill. Air Spring Filling or Refolding Instructions for entering diagnostics and test descriptions follow.

Air Suspension On/Off Switch:

1. Turn On the air suspension switch. Diagnostic pigtail is to be UNGROUNDED.
2. Install battery charger to reduce battery drain.
3. Cycle the ignition from the OFF to RUN position, hold in the RUN position for a minimum of five seconds, then return to the OFF position. Driver's door is OPEN with all other doors SHUT.
4. Change the diagnostic pigtail from an UNGROUNDED state to a GROUNDED state by attaching a lead from the diagnostic pigtail to vehicle ground. The pigtail must remain GROUNDED during the spring fill sequence.

Figure 27:

5. Turn the ignition switch to the RUN position. (Do not start vehicle). The warning lamp will blink continuously at a rate of 1.8 blinks per second to indicate diagnostics has been entered and is ready.
6. CLOSE, then OPEN the driver's door ONCE to initiate Test 1. The warning lamp will blink ONE, pause, blink, pause, etc. until the next test is started.
7. Each successive transition from door CLOSED to door OPEN will cause the module to advance to the next step in the test sequence. The warning lamp will blink the current test number.

Terminating Diagnostics
Diagnostics may be terminated and the module returned to the normal operational mode at any time by CYCLING the ignition, ACTUATING the brake or UNGROUNDING the diagnostic pigtail.

Test Description
The following tests will be run during Diagnostics. For Tests 1,2 and 3, PASS/FAIL will be determined by the module at the conclusion of Step A, B or C. The following Steps occur in each of the first three Tests:
A. Raise the (rear, right front, left front) of the vehicle for 15 seconds. Continue raising vehicle for an additional 15 seconds (30 seconds total maximum) or until a 'Vehicle High' signal, or an illegal sensor read is received from the (rear, right front, left front) sensor.
B. Lower the (rear, right front, left front) of vehicle for 30 seconds or until a 'Vehicle Low' signal, or an illegal sensor read is received from the (rear, right front, left front) sensor.
C. Raise the (rear, right front, left front) of vehicle 30 seconds or until a 'Vehicle Trim' signal, or an illegal sensor read is received from the (rear, right front, left front) sensor.

If the expected signal is not received within the 30 second limit, the test will stop and the warning lamp will turn on continuously. Also, if an illegal sensor read is received, the test will stop and the warning lamp will flash rapidly.

The failed test may then be repeated by CLOSING/OPENING the door or the next test may be initiated by CLOSING/OPENING the door twice within 15 seconds.
Test 1 Rear Suspension.
Test 2 Right Front Suspension.
Test 3 Left Front Suspension.

NOTE: For Tests 4 through 10, PASS/FAIL will be determined by the technician observing the operation of the specific component.

Test 4 Compressor is cycled ON/OFF at 0.25 Hz. The compressor is limited to cycling a maximum of 50 times.
Test 5 Vent solenoid is cycled OPEN/CLOSED at 1 Hz.
Test 6 Left front solenoid is cycled OPEN/CLOSED at 1 Hz and the vent solenoid is opened. Left front corner of the vehicle will drop slowly as test progresses.
Test 7 Right front solenoid is cycled OPEN/CLOSED at 1 Hz and the vent solenoid is opened. Right front corner of the vehicle will drop slowly as test progresses.
Test 8 Right rear solenoid is cycled OPEN/CLOSED at 1 Hz and the vent solenoid is opened. Right rear corner of the vehicle will drop slowly as test progresses.
Test 9 Left rear solenoid is cycled OPEN/CLOSED at 1 Hz and the vent solenoid is opened. Left rear corner of the vehicle will drop slowly as test progresses.
Test 10 ACTUATING the brake, turning the ignition switch OFF, or DISCONNECTING the diagnostic lead returns the module from diagnostics to the normal operating mode.
Turn the ignition switch OFF, and DISCONNECT and remove the diagnostic ground lead in the luggage compartment.

Diagnostic Testing Index
Section A: Perform System Diagnostic Test
Section B: Cannot Enter/Sequence or Exit Diagnostic Test
Section C: Diagnose Sensor Related Problem
Section D: Diagnose Vehicle Rear Problem
Section E: Diagnose Vehicle Right Front Problem
Section F: Diagnose Vehicle Left Front Problem
Section G: Diagnose Compressor Motor Electrical Problem
Section H: Diagnose Compressor Vent Solenoid Electrical Problem