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 three modes that are described below:

    • DTC Information: In this mode, current or history DTC(s) stored by the EBTCM 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
       - ABS activity status
       - TCS activity status
       - 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 EBTCM can be cleared.

Data Display

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

    • ABS Data
    • TCS Data
    • VES Data

A brief description of all ABS and TCS data parameters available on the scan tool are listed below:

ABS Data:

    • 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.
    • Engine Speed--scan tool displays: 0 to 10200 RPM--This is essentially a digital tachometer display.
    • ABS Warning Lamp--scan tool displays: ON/OFF--This indicates the state of the ANTILOCK indicator.
    • TCS Warning Lamp--scan tool displays: ON/OFF--This indicates the state of the TRAC OFF indicator.
    • Low Traction Lamp--scan tool displays: ON/OFF--This indicates the state of the LOW TRAC indicator.
    • ABS Active--scan tool displays: YES/NO--This parameter indicates if the ABS is currently in a ABS event or not.
    • TCS Active--scan tool displays: YES/NO--This parameter indicates if the TCS is currently in a TCS event or not.
    • Brake Switch--scan tool displays: Applied/Released--This parameter indicates the state of the brake switch.
    • Ignition Voltage--scan tool displays: Volts--This parameter is the ignition voltage at the EBTCM.
    • Valve Relay State--scan tool displays: ON/OFF--This parameter indicates the state of the valve relay.
    • Motor Relay State--scan tool displays: ON/OFF--This parameter indicates the state of the return pump relay.
    • LF Inlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.
    • LF Outlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.
    • RF Inlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.
    • RF Outlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.
    • LR Inlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.
    • LR Outlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.
    • RR Inlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.
    • RR Outlet Valve Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.

TCS Data:

    • Engine Speed--scan tool displays: 0 to 10200 RPM--This is essentially a digital tachometer display.
    • EBTCM to PCM Requested Torque--scan tool displays: -100 to 510N·m--This parameter represents the requested engine torque from the EBCTM to the PCM.
    • PCM to EBTCM Delivered Torque--scan tool displays: -100 to 510N·m--This parameter represents the delivered engine torque from the PCM to the EBTCM.
    • Rough Road Parameter--scan tool displays: g (gravity)--This parameter, calculated from wheel speed sensor data, represents the rapid variation or acceleration in g's of the driven wheel speeds due to a rough road. A rough road will cause torque to be applied to the drivetrain which may be detected by the PCM's OBD II misfire diagnostic as a false misfire. This rough road detection data is sent to the PCM via serial data. The PCM will disable the OBD II misfire diagnostic during rough road detection since this could be interpreted as misfire.
    • TCS Switch State--scan tool displays: Pressed/Released--This parameter indicates the state of the traction control switch.
    • Low Traction Lamp--scan tool displays: ON/OFF--This indicates the state of the LOW TRAC indicator.
    • TCS Warning Lamp--scan tool displays: ON/OFF--This indicates the state of the TRAC OFF indicator.
    • TCS Active--scan tool displays: YES/NO--This parameter indicates if the TCS is currently in a TCS event or not.
    • LF TCS Prime Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.
    • RF TCS Prime Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.
    • LF TCS Isolation Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.
    • RF TCS Isolation Solenoid--scan tool displays: Active/Inactive--This display indicates the commanded state of the solenoid valve.

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 set a DTC.

Special 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, or ABS/TCS, the Special Functions are as following:

ABS

    • Solenoid Test ( inlet solenoid valves)
    • Solenoid Test (outlet solenoid valves)

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 RUN.
  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 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 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 RUN.
  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 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.