Accessing Trouble Codes

Data Link Connector (DLC):

The New Generation STAR Tester (NGS) or equivalent must be used to access Diagnostic Trouble Codes (DTCs). Connect tester to the Diagnostic Link Connector (DLC) found under left side of instrument panel and follow tool manufacturer's instructions for operation of the tool.

After accessing and recording any DTC, refer to Diagnostic Trouble Code Interpretation to locate faulty component or system.

DIAGNOSTIC PROCEDURES, INSTRUCTIONS & TEST MODES
Diagnostic test and repair services should be performed in a set sequence to properly access all DTCs and to complete repairs without masking problems or performing redundant procedures. The correct order of accessing DTCs are as follows:
1. Retrieve/Clear Continuous DTCs.
2. On Demand Self Test.
3. Pneumatic Test.

If different DTCs are found in each testing sequence, malfunctions found should be corrected in the following order.
1. On Demand Self Test.
2. Pneumatic Test
3. Retrieve/Clear Continuous DTCs.

DTCs generated in any testing sequence except Continuous DTC mode are not stored in memory. Any DTC stored will be cleared from memory after 80 ignition key cycles from its last occurrence. When multiple DTCs are generated that relate to the same system, always start testing and repairs at the root of the system, then proceed down to the individual component.

There are five individual diagnostic test modes and one monitoring mode available to the technician as follows:
1. Retrieve/Clear Continuous DTCs.
2. On Demand Self Test.
3. Accurate Trim Test.
4. Pneumatic Test.
5. Wiggle Test.
Select the correct sequence to best diagnose the conditions as described by the owner/operator.

Retrieve/Clear Continuous DTCs
This menu option is used to retrieve any DTC that may have been stored in control unit memory. Connect tester per tool manufacturer's instructions to the DLC found under left side of instrument panel, then follow tool manufacturer's instructions to access this menu option.

On Demand Self Test
This menu option is used to run a pre-programed series of tests to the suspension electrical system. Any DTCs generated by system faults during this test will not be stored in control unit memory. This test series should always be run after any repairs have been performed on the suspension system.

Connect tester per tool manufacturer's instructions to the DLC found under left side of instrument panel, then follow tool manufacturer's instructions to access this menu option.

This menu option is used to bring each corner of the vehicle to within plus/minus 2 mm of a predetermined height. Select this menu option when performing ride height measurements or performing wheel alignment. DTCs will not be displayed in this mode unless it is generated by a system fault during accurate trim test operation.

Pneumatic Test
This menu option is used to exercise and test the pneumatic components and height sensors of the suspension system. Each suspension unit is pumped then vented for five seconds, in turn, while being monitored by the vehicle control unit. If a suspension unit fails, a DTC is generated recognizing the suspected component or system. The generated DTC is not stored in control unit memory.

It should be noted that some compressor relay system short circuit faults and some height sensor open circuit faults may be recognized as a pneumatic system problem, proper component and circuit testing should be performed before component replacement.

Connect tester per tool manufacturer's instructions to the DLC found under left side of instrument panel, then follow tool manufacturer's instructions to access this menu option.

Wiggle Test
This menu option is used to allow the technician to test individual components, connectors and circuits for intermittent problems. The tester monitors system signals and will emit an audible tone and increment an incidence counter when it notices a change in those signals.

Connect tester per tool manufacturer's instructions to the DLC found under left side of instrument panel, then follow tool manufacturer's instructions to access this menu option.

PID/Data Monitor & Record
This menu option is used to used to monitor control unit inputs and outputs on a real-time basis. This can be useful during diagnosis as an aid to understanding why a system is acting in particular manner.

Connect tester per tool manufacturer's instructions to the DLC found under left side of instrument panel, then follow tool manufacturer's instructions to access this menu option.


Active Command Modes, Semi-Active Ride Control
This menu option is used to allow the technician to control the ON (soft ride) and OFF (firm ride) position of each shock absorber, allowing checking of shock unit condition and comparison of shock units.

This mode is also useful while diagnosing an intermittent problem in a shock unit. Turn ON a shock solenoid, then by listening for solenoid clicking while moving components, connectors and harness, opens and shorts can be located.

Connect tester per tool manufacturer's instructions to the DLC found under left side of instrument panel, then follow tool manufacturer's instructions to access this menu option.

Air Suspension Diagnostic Control
The vent solenoid is turned ON and the suspension solenoids are turned OFF automatically when the compressor is turned ON to reduce compressor load.

This menu option is used to allow the technician to manually control the pumping and venting of individual suspension units. This can be useful when diagnosing sticking or leaking pneumatic components.

This mode also allows technician control of the vent and air spring solenoids, the CHECK RIDE CONTROL message and the height sensor circuit power. This can be useful when diagnosing intermittent problems in these circuits. It is also useful during component replacement, it allows venting of individual units to facilitate service.

Connect tester per tool manufacturer's instructions to the DLC found under left side of instrument panel, then follow tool manufacturer's instructions to access this menu option.

Function Tests
This menu option is used to allow the technician to perform ride height calibration. This mode allows the technician to input new ride height calibrations into the control unit to compensate for permanent additions to or subtractions from the vehicle which would affect the ride height. This precludes the necessity of mechanical adjustment of ride height sensors.

Connect tester per tool manufacturer's instructions to the DLC found under left side of instrument panel, then follow tool manufacturer's instructions to access this menu option.