For 1990-2009 cars

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:

• | DTC Information: In this mode, current or history DTC(s) stored by the EBCM can be displayed.

• | Enhanced Data: In this mode, DTC data for current or history DTC(s) is displayed. This data includes the following information at the time when the DTC(s) was set:

- | Brake switch status

- | TCS switch status (if equipped)

- | ABS activity status

- | TCS activity status (if equipped)

- | Vehicle speed

- | The number drive cycles since the DTC was set

• | Clear DTC Information: In this mode, current or history DTC(s) stored by the EBCM can be cleared.

### Snapshot

In this mode, the scan tool 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 mode, the scan tool can be used to perform functional tests on the ABS/TCS 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/TCS, the Special Functions are as following:

• | Automated Bleed Procedure

• | ABS Relay Test

• | Automated Test

• | Solenoid Tests

- | Right Rear Inlet Valve Solenoid

- | Right Rear Outlet Valve Solenoid

- | Right Front Inlet Valve Solenoid

- | Right Front Outlet Valve Solenoid

- | Left Rear Outlet Valve Solenoid

- | Left Rear Inlet Valve Solenoid

- | Left Front Inlet Valve Solenoid

- | Left Front Outlet Valve Solenoid

### Lamp Test

In order to do a lamp test, you must use the scan tool and be in the Instrument Panel Cluster Special Functions. Then go to WOW mode, in this mode you can turn all the indicators ON and OFF.

• | ABS Indicator

• | TRAC OFF indicator

• | LOW TRAC indicator

• | Brake Warning indicator

The WOW Test aids in diagnosing indicator malfunctions. The test allows the operator to flash the all the indicators on and off.

### Automated Test

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

1. Turn OFF the ignition.
2. Install a scan tool.
3. Turn ON the ignition, with the engine OFF.
4. Select the scan tool's Special Functions.
5. Select the Automated Test.
6. Run the Automated Test.
7. Observe any DTCs set.

### Solenoid Tests (Inlet Valves)

The Solenoid Test for inlet valves 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 ABS operating conditions because the EBCM has determined that the wheel is moving too slowly. Thus, it will hold 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. Turn OFF the ignition.
2. Install a scan tool.
3. Turn ON the ignition, with the engine OFF.
4. Raise vehicle such that wheels are about 6 inches off the floor with the transmission in neutral. Refer to Lifting and Jacking the Vehicle

in General Information for lifting.

5. Select the scan tool's Special Functions.
6. Select 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.

### Solenoid Tests (Outlet Valves)

The Solenoid Test for outlet valves activates the selected hydraulic wheel circuit valves, placing them 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 valves 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. Turn OFF the ignition.
2. Install a scan tool.
3. Turn ON the ignition, with the engine OFF.
4. Raise vehicle such that wheels are about 6 inches off the floor with the transmission in neutral. Refer to Lifting and Jacking the Vehicle in General Information for lifting.
5. Have an assistant press and hold the brake pedal.
6. Select the scan tools Special Functions.
7. Select 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.