Diagnostic Routine X

Diagnostic Routine X

Diagnostic Overview

C0020:01, 1C or 71

Refer to Wiring Diagram Set 42 for schematic and connector information Electrical Diagrams.

Normal Operation and Fault Conditions

The ABS (Anti-Lock Brake System) module uses an internal solid state switch to operate the hydraulic pump motor. The ABS (Anti-Lock Brake System) module tests the hydraulic pump motor by activating it for 30 milliseconds. While the pump motor is being activated, the ABS (Anti-Lock Brake System) module monitors the voltage drop across the hydraulic pump motor. After 30 milliseconds have passed, the ABS (Anti-Lock Brake System) module stops applying voltage to the pump motor and monitors the voltage that the spinning hydraulic pump motor is generating and the voltage drop across the hydraulic pump motor solid state switch. If the monitored voltages are not within the specifications, the ABS (Anti-Lock Brake System) module sets one or more DTCs (Diagnostic Trouble Codes).

DTC Fault Trigger Conditions






Visual Inspection and Diagnostic Pre-checks

- Make sure the vehicle battery terminals and cables are free of any corrosion and other contaminates.

- Make sure the vehicle battery terminals are tightened to their correct torque specifications.

- Make sure BJB (Battery Junction Box) fuse 7 (40A) and the fuse socket are OK.

Pinpoint Test

1. CHECK THE ABS (Anti-Lock Brake System) MODULE DTCs (Diagnostic Trouble Codes)

1. Using a scan tool, carry out the ABS (Anti-Lock Brake System) module self-test.

2. Retrieve and record all ABS (Anti-Lock Brake System) module DTCs (Diagnostic Trouble Codes).

Is DTC (Diagnostic Trouble Code) C0020:71 present?






2. CHECK PUMP MOTOR OPERATION

1. Using a scan tool, activate the ABS (Anti-Lock Brake System) pump motor (PMP_MTR) active command.

2. Listen for the ABS (Anti-Lock Brake System) pump motor noise.

Does the ABS (Anti-Lock Brake System) pump motor run for approximately 2 seconds?






3. CHECK FOR FAULT REPEATABILITY

1. Using a scan tool, clear the ABS (Anti-Lock Brake System) module DTCs (Diagnostic Trouble Codes).

2. Ignition OFF.

3. Ignition ON.

4. Test drive the vehicle at speeds greater than 20 km/h (12 mph) and carry out at least 1 ABS (Anti-Lock Brake System) stop.

5. Ignition OFF.

6. Ignition ON.

7. Using a scan tool, carry out the ABS (Anti-Lock Brake System) module self-test.

8. Retrieve and record all ABS (Anti-Lock Brake System) module DTCs (Diagnostic Trouble Codes).

Are any ABS (Anti-Lock Brake System) module DTCs (Diagnostic Trouble Codes) retrieved?






4. CHECK THE PUMP MOTOR VOLTAGE SUPPLY TO THE ABS (Anti-Lock Brake System) MODULE

1. Ignition OFF.

2. Disconnect ABS (Anti-Lock Brake System) Module electrical connector.

3. Measure:





Is the voltage greater than 11 volts?






5. CHECK THE ABS (Anti-Lock Brake System) MODULE GROUND CIRCUIT FOR AN OPEN

1. Ignition OFF.

2. Disconnect the battery negative cable. REFER to Battery Disconnect

3. Measure:





Is the resistance less than 3 ohms?






6. CHECK FOR CORRECT ABS (Anti-Lock Brake System) MODULE OPERATION

1. Ignition OFF.

2. Disconnect and inspect the ABS (Anti-Lock Brake System) Module electrical connector (if not previously disconnected).

3. Repair:

- corrosion (install new connector or terminal - clean module pins)
- damaged or bent pins - install new terminals/pins
- pushed-out pins - install new pins as necessary

4. Connect the ABS (Anti-Lock Brake System) Module electrical connector. Make sure it seats and latches correctly.

5. Operate the system and determine if the concern is still present.

Is the concern still present?