Scan Tool Testing and Procedures

When using the Tech 1 scan tool for ABS/ASR system diagnostics, the ABS and ASR systems are disabled and the Service ABS and Service ASR indicator lamps will be illuminated. Normal power assisted braking is still applicable. After completion of all diagnostic procedures, turn the ignition switch Off for at least 10 seconds and disconnect Tech 1 tool, then the system will return to normal operation. The valve solenoid relay is turned Off by the EBCM when a code is set. When monitoring the data list with the Tech 1, the valve solenoid relay will be noted as Off, this is normal and should not be considered a system problem. Also when monitoring the data list, the throttle angle readings may stop updating. This is normal and should not be considered as system problem.
The Tech 1 has five test modes for diagnosis and testing of the ABS/ASR system as follows:
1. Mode F0 - Data List: Tech 1 monitors wheel speed data and brake switch status.
2. Mode F1 - Code History: In this mode, fault code history is displayed and includes the number of ignition cycles since the codes was set and other system information. Up to three codes are included in the ABS history data.
3. Mode F2 - Trouble Codes: In this test, trouble codes stored by the EBCM may be displayed or cleared.
4. Mode F3 - Snapshot: In this test, displays data before and after a snapshot triggering condition which may not set a code.
5. Mode F4 - Miscellaneous Tests: In this mode, the Tech 1 performs modulator valve assembly functional tests, lamp output tests, pilot valve tests and ASR tests to assist in problem isolation during diagnostics.
6. Mode F5 - TPS Learn: If the TPS or throttle body has been replaced, the EBCM must learn the TPS idle position voltage. This is required to ensure effective engine torque reduction during ASR operation.

MODE F3: SNAPSHOT

Conditions that will trigger the Tech 1 snapshot feature are as follows:
1. Loss of serial data.
2. Valve solenoid relay less then 11 volts (low voltage.)
3. Valve solenoid relay Off, less then two volts (relay will be Off if codes are set).
4. One wheel speed sensor ±8 mph of others (intermittent wheel speed).
5. Three wheel speed sensor ±3 mph of each other and one ±5 mph of the others (wheel speed out of range).
6. Low brake fluid.
7. Lateral accelerometer greater then 4.35 or less then 1.05 volts (out of range).
8. System voltage more then 17 volts (high voltage).
9. Sudden engine RPM change greater then 1100 RPM (intermittent engine RPM).
10. Brake switch state change of On-Off-On in less then 200 milliseconds (intermittent brake switch).

MODE F4: ABS TESTS

AUTO Test

The auto test cycles each valve solenoid, pump motor and relays to inspect component operation. This test is the same as the auto test the system performs when vehicle speed reaches 4 mph in forward or reverse. Stored codes will be indicated upon completion of the test.
1. With ignition switch in Off position.
2. Connect Tech 1 scan tool with appropriate brake cartridge.
3. Turn ignition switch to On position.
4. Select F4, Misc Tests.
5. Select F1, Auto Test.
6. Depress enter key to run auto test.
7. Record any stored codes.

Valve Solenoid-Pressure Hold

The pressure hold test activates the hydraulic wheel circuit valve in the pressure hold position. In that position the valve will not allow master cylinder pressure to be delivered to the wheel circuit. In this test, the tech 1 tool operates the valve to the pressure position which will allow wheel movement with brake pedal application.
1. With ignition switch in Off position.
2. Connect Tech 1 scan tool with appropriate brake cartridge.
3. Turn ignition switch to On position.
4. Raise and support vehicle with wheels about six inches from floor.
5. Select valve solenoid test, then depress Tech 1 tool HOLD PRESSURE.
6. Depress brake pedal.
7. Attempt to turn rear wheel, movement should be indicated.

Valve Solenoid-Pressure Reduction

The pressure reduction test activates the hydraulic wheel circuit valve, placing it in the pressure reduce position. In that position, the valve allows caliper pressure to return to the master cylinder. During this test the wheel should be moveable with brake pressure applied.
1. With ignition switch in Off position.
2. Connect Tech 1 scan tool with appropriate brake cartridge.
3. Turn ignition switch to On position.
4. Raise and support vehicle with wheels about six inches from floor.
5. Have an assistant depress brake pedal.
6. Select valve solenoid test, then depress Tech 1 tool RELEASE PRESSURE.
7. Depress brake pedal, turn rear wheel, movement should be indicated.

Lamp Test

The lamp test is used to inspect the Service ABS, Service ASR, ABS Active, ASR Active and ASR Off lamp operation.
1. With ignition switch in Off position.
2. Connect Tech 1 scan tool with appropriate brake cartridge.
3. Turn ignition switch to On position.
4. Select F4, Misc Tests.
5. Select F2, Lamp Test.
6. Select lamp to be tested.
7. Depress up arrow to turn lamp On and down arrow to turn lamp Off.

Pilot Valve Test

The test indicates whether the pilot valve in the modulator valve assembly moves to the position which blocks pressure to the master cylinder. The pilot valve blocks pressure to the master cylinder before pump motor activation and fluid pressure application to the rear wheel circuits during ASR activation.
1. With ignition switch in Off position.
2. Connect Tech 1 scan tool with appropriate brake cartridge.
3. Turn ignition switch to On position.
4. Raise and support vehicle with wheels about six inches from floor.
5. Select F4, Misc Tests.
6. Select F3, Pilot Vlv Test.
7. Have assistant depress Tech 1 up arrow, then depress and hold brake pedal.
8. Attempt to move rear wheel by hand, no movement should be indicated.

ASR Test

The ASR test runs the pump motor to apply fluid pressure to the rear wheel circuits. The ``Pilot Valve Test'' as outlined previously must be run prior to the ASR test.
1. With ignition switch in Off position.
2. Connect Tech 1 scan tool with appropriate brake cartridge.
3. Turn ignition switch to On position.
4. Raise and support vehicle with wheels about six inches from floor.
5. Select F4, Misc Tests.
6. Select F4, ASR Test.
7. Perform pilot valve test to confirm valve operation.
8. Depress up arrow to begin ASR test.
9. Attempt to move rear wheel by hand, no movement should be indicated.

MODE 5: TPS LEARN

When a throttle position sensor or throttle body assembly are replaced the TPS must relearn the TPS idle position voltage.
1. Place ignition switch in Off position.
2. Connect Tech 1 scan tool with appropriate brake system cartridge.
3. Turn ignition switch On.
4. Follow menus to reach ABS/ASR feature.
5. Select F5, TPS LEARN.
6. Depress up arrow to begin learn procedure.
7. Wait for Tech 1 tool to indicate COMPLETE.
8. Disconnect Tech 1 scan tool.