Refer to the Scan Tool Manual for complete information on scan tool diagnostics.

Diagnostic Trouble Codes (DTC)

The Diagnostic Trouble Codes (DTC) function has three modes that are described below:

Data Display

The Data Display function contains two sets of menus. The menus available depend on the number and type of systems on the vehicle and are listed below:

A brief description of all ABS/TCS/Active Handling (if equipped with RPO JL4) data parameters available on the scan tool are listed below:

Snapshot

In this test mode, the scan tool can captures the data listed in the data displays before and after a snapshot--triggering condition which may or may not set a DTC.

Special Functions

In this test mode, the scan tool can be used to perform functional tests on the system which help verify proper operation. Malfunction conditions can be further identified by testing and observing the test results. DTCs must be cleared before any tests in Special Functions can be performed. The Special Functions are grouped as follows:

The Special Functions are detailed below.

The Automated Test cycles each valve solenoid and the pump motor (as well as the necessary relays) to check component operation. If a malfunction is detected, the EBTCM will set DTC(s), which will be displayed upon completion of the test. Perform the test as follows:

1. Ignition OFF.
2. Install the scan tool.
3. Turn ignition to ON.
4. Select the scan tool's Special Functions.
5. Select the Automated Test.
6. Run the Automated Test.
7. Note any DTCs set.

The Pressure Hold Mode activates the selected wheel circuit Inlet valve placing it in the pressure hold position. When in the pressure hold position, the valve will not allow master cylinder pressure to be delivered to the hydraulic wheel circuit. This is done under actual operating conditions because the EBTCM has determined that the wheel is moving too slowly, so it holds additional master cylinder pressure from it in an attempt to allow it to rotate at an appropriate speed. The scan tool commands the valve to close, which should allow the technician to spin the wheel even though an assistant is applying pressure to the brake pedal. Perform the test as follows:

1. Ignition OFF.
2. Install the scan tool.
3. Turn ignition to ON.
4. Raise vehicle such that wheels are about 6 inches off the floor with the transmission in neutral.
5. Select the scan tool's Special Functions.
6. Select Valve Solenoid Test. Have an assistant command Hold Pressure with the scan tool.
7. Have the assistant press and hold the brake pedal.
8. Attempt to move the wheel being tested by hand; it should move even though the assistant is applying pressure to the brake pedal. The wheels may be difficult to turn by hand, but can be moved if the system is working properly.

The Pressure Release Mode activates the selected hydraulic wheel circuit valves, placing them in the pressure reduce position. When in the pressure reduce position, the valve will allow wheel caliper pressure to be returned to the master cylinder circuit. This is done under actual operating conditions because the EBTCM has determined that the wheel is moving too slowly, and holding additional master cylinder pressure from it has not allowed it to rotate at an appropriate speed. The scan tool commands the valves to these positions which should allow the technician to spin the wheel even though an assistant is applying pressure to the brake pedal. Perform the test as follows:

1. Ignition OFF.
2. Install the scan tool.
3. Turn ignition to ON.
4. Raise vehicle such that wheels are about 6 inches off the floor with the transmission in neutral.
5. Have an assistant press and hold the brake pedal.
6. Select the scan tools Special Functions.
7. Select Valve Solenoid Test. Have the assistant command Release Pressure with the scan tool.
8. Attempt to move the wheel being tested by hand; it should move even though the assistant is applying pressure to the brake pedal. The wheels may be difficult to turn by hand, but can be moved if the system is working properly.

This test runs the pump motor to apply fluid pressure to the rear wheel circuits.

Perform the test as follows (this test does NOT require an assistant):

1. Ignition OFF.
2. Install the scan tool.
3. Turn ignition to ON.
4. Raise vehicle so that wheels are about 6 inches off the floor with the transmission in neutral.
5. Select the scan tools Special Functions.
6. Select TCS Test.
7. Command the TCS Test on with the scan tool. The pump motor will turn on for approximately 25 seconds.
8. Attempt to move each rear wheel by hand, they should not move, due to the pump motor running and applying pressure to the rear wheels.

This test monitors the analog and digital steering angle position and can only be run after the Steering Wheel Position Sensor has been centered.

Perform the test as follows:

1. Ignition OFF.
2. Install the scan tool.
3. Start the engine.
4. Ensure the steering wheel is in a straight position.
5. Carefully drive the vehicle in a straight line for 45 seconds at 24 km/h (15 mph) while monitoring the Steering Wheel Position Centering Angle on the scan tool.
6. When centered the scan tool will indicate YES.
7. Stop the vehicle and leave the engine running.
8. Select the scan tools Special Functions.
9. Select Steering Position Sensor Test on the scan tool.
10. While monitoring the Steering Position Sensor Test using the scan tool, turn the steering wheel to the left until it can go no further, then turn the steering wheel to the right until it can turn no further (lock to lock) three times. Read the scan tool each time the wheels are straight and the steering wheel is at its center position. This reading should always be near zero for the digital and analog display (5 degrees of each other).