GM Service Manual Online
For 1990-2009 cars only

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

Diagnostic Trouble Codes (DTC)

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

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

Data Display

The Data Display function contains a list of ABS and TCS data parameters. A brief description of all ABS/TCS data parameters available on the scan tool are listed below:

    • Left Front Wheel Speed--scan tool displays: Km/h / MPH--Display shows actual wheel speed.
    • Right Front Wheel Speed--scan tool displays: Km/h / MPH--Display shows actual wheel speed.
    • Left Rear Wheel Speed--scan tool displays: Km/h / MPH--Display shows actual wheel speed.
    • Right Rear Wheel Speed--scan tool displays: Km/h / MPH--Display shows actual wheel speed.
    • Delivered Engine Torque--scan tool displays: 0 to 100 %--This parameter represents the delivered engine torque from the ECM to the EBTCM.
    • Engine Speed--scan tool displays: Engine RPM--This is essentially a digital tachometer display.
    • Valve Relay--scan tool displays: Valve Relay Volts--This parameter indicates the switched volts of the valve relay.
    • Valve Relay State--scan tool displays: On/Off--This parameter indicates the state of the valve relay.
    • Return Pump Relay--scan tool displays: On/Off--This parameter indicates the state of the return pump relay.
    • Battery Voltage--scan tool displays: Battery Volts--This parameter is the battery voltage at the EBTCM.
    • Brake Lamp Switch State--scan tool displays: On/Off--This parameter indicates the state of the brake switch.
    • TCS Switch State--scan tool displays: On/Off--This parameter indicates the state of the traction control switch.
    • Left Front Inlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve
    • Left Front Outlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve
    • Right Front Inlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve
    • Right Front Outlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve
    • Left Rear Inlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve
    • Left Rear Outlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve
    • Right Rear Inlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve
    • Right Rear Outlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve
    • Left Front Valve Solenoids--scan tool displays: Hold/Release/Apply--This display indicates the commanded state of the combined inlet and outlet valves for this particular wheel. This parameter give an indication of the hydraulic mode of the solenoid valves.
    • Right Front Valve Solenoids--scan tool displays: Hold/Release/Apply--This display indicates the commanded state of the combined inlet and outlet valves for this particular wheel. This parameter give an indication of the hydraulic mode of the solenoid valves.
    • Left Rear Valve Solenoids--scan tool displays: Hold/Release/Apply--This display indicates the commanded state of the combined inlet and outlet valves for this particular wheel. This parameter give an indication of the hydraulic mode of the solenoid valves.
    • Right Rear Valve Solenoids--scan tool displays: Hold/Release/Apply--This display indicates the commanded state of the combined inlet and outlet valves for this particular wheel. This parameter give an indication of the hydraulic mode of the solenoid valves.

Special Functions

In this test 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. The Special Functions are listed below:

    • Automated Test
    • Solenoid Tests (for all inlet and outlet solenoid valves)
    • Lamp Tests

The Special Functions are detailed below.

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 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 the ON position.
  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 Solenoid Tests. Have an assistant command ON to 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 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 the ON position.
  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 Solenoid Tess. Have the assistant command ON to 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.

Lamp Tests

This test allows activation of the ABS indicator.

The Lamp Test aids in diagnosing indicator malfunctions. The test allows the operator to flash the indicator on and off manually.

Automated Test

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 the ON position.
  4. Select the scan tool's Special Functions.
  5. Select the Automated Test.
  6. Run the Automated Test.
  7. Note any DTCs set.

Snapshot

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