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

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

The Data Display function contains two special function "hot keys," and a data list which details ABS parameters. The hot keys perform the following functions:

In this test mode, the scan tool can be used to perform functional tests on the ABS 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. In a vehicle equipped with ABS, the Special Functions are grouped as following:

Function Test

The Function 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 EBCM 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 RUN.
4. Select the scan tool's Special Functions.
5. Select the Function Test.
6. Run the Function Test.
7. Note any DTCs set.

Automated Bleed

Automated Bleed cycles each valve solenoid and the pump motor in a special sequence (as well as the necessary relays) in order to bleed air out of the BPMV after removal or installation of brake lines, or BPMV replacement. Perform the test as follows:

1. Ignition OFF.
2. Install the scan tool.
3. Turn ignition to RUN.
4. Select the scan tool's Special Functions.
5. Select the Automated Bleed function.
6. Run the Automated Bleed function.

ABS Motor

This function tests the ABS pump motor to check component operation. If a malfunction is detected, the EBCM will set DTC(s), and the ABS indicator lamp will turn on. Perform the test as follows:

1. Ignition OFF.
2. Install the scan tool.
3. Turn ignition to RUN.
4. Select the scan tool's Special Functions.
5. Select the ABS Motor Test.
6. Run the ABS Motor Test.

System Identification

This function is used to identify the hardware and software revision of the EHCU

1. Ignition OFF.
2. Install the scan tool.
3. Turn ignition to RUN.
4. Select the scan tool's Special Functions.
5. Select System Identification.
6. Make note of the relevant information.

Tire Size Calibration

This function allows the EBCM tire size to be set or changed when a new EBCM is installed, or different tires/wheels are installed on the vehicle.

1. Ignition OFF.
2. Install the scan tool.
3. Turn ignition to RUN.
4. Select the scan tool's Special Functions.
5. Select the Tire Size Calibration.
6. Make the necessary changes to existing tire size setting.

ABS Lamp

This test allows activation of the ABS indicator. The ABS Lamp test aids in diagnosing indicator malfunctions. The test allows the operator to turn the indicator on and off manually.

BRAKE Lamp

This test allows activation of the BRAKE indicator. The BRAKE Lamp test aids in diagnosing indicator malfunctions. The test allows the operator to flash the indicator on and off manually.

Solenoid Tests (Isolation Valves)

The Solenoid Test for isolation valves activates the selected wheel circuit Isolation 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 ABS operating conditions because the EBCM 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 RUN.
4. Raise the vehicle such that wheels are about 15 cm (6 in) off the floor with the transmission in neutral.
5. Select the scan tool's Special Functions.
6. Select the desired Isolation Solenoid test. Have an assistant command the Isolation valve ON 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.

Solenoid Tests (Dump Valves)

The Solenoid Test for Dump valves activates the selected hydraulic wheel circuit Dump valve, placing it in the pressure release position. When in the pressure release position, the valve will allow wheel caliper pressure to be returned to the master cylinder circuit. This is done under ABS operating conditions because the EBCM 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 valve to release hydraulic pressure to the affected brake caliper, 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 RUN.
4. Raise the 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 the desired Dump Solenoid Test. Have the assistant command the Dump valve ON 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.

ABS Relay

This function tests the ABS relay to check component operation. If a malfunction is detected, the EBCM will set DTC(s), and the ABS indicator lamp will turn on. Perform the test as follows:

1. Ignition OFF.
2. Install the scan tool.
3. Turn ignition to RUN.
4. Select the scan tool's Special Functions.
5. Select the ABS Relay.
6. Take note of the relay status as the relay is cycled.

In this test mode, the scan tool captures the data listed in the data displays before and after a snapshot. The following triggering conditions are available: