Pinpoint Test R: DTCs C0020:15, C0020:71
Anti-Lock Control - Four-Channel
Pinpoint Tests
Pinpoint Test R: DTCs C0020:15, C0020:71
Refer to Wiring Diagram Set 42, Vehicle Dynamic Systems for schematic and connector information. Diagrams By Number
Normal Operation
The ABS module uses an internal solid state switch to operate the ABS pump motor. When the engine speed is above 700 rpm or the vehicle speed is at approximately 7 km/h (4 mph), the ABS module tests the ABS pump motor by activating it for 30 milliseconds. While the pump motor is being activated, the ABS module monitors the voltage drop across the ABS pump motor solid state switch and the amount of current the ABS pump motor draws through the solid state switch. If the voltage drop is too high or if the ABS pump motor is drawing too much current, the ABS module sets a DTC. After 30 milliseconds have passed, the ABS module stops applying voltage to the pump motor and observes the voltage that the spinning ABS pump motor is generating. The voltage generated by the motor indicates how fast the motor is spinning. A voltage that is too low indicates the motor is not spinning freely and a DTC sets.
When these DTCs set, the ABS module takes the following actions:
- ABS braking is disabled
- Traction control braking is disabled (although Engine Only Traction Control (EOTC) is still available)
- Stability assist is disabled
Fused battery voltage from Battery Junction Box (BJB) fuse 96 (50A) is used by the ABS module to power the ABS pump motor. Insufficient power or ground causes multiple DTCs to set.
- DTC C0020:15 (ABS Pump Motor Control: Circuit Short to Battery or Open) - sets when the ABS pump motor voltage feedback is greater than 0.75 volts for more than 50 milliseconds, if there is an open or high resistance on the ABS pump motor circuit between the ABS module and the Hydraulic Control Unit (HCU), or if the ABS module is faulted internally.
- DTC C0020:71 (ABS Pump Motor Control: Actuator Stuck) - sets when the ABS module detects that the ABS pump motor is not rotating when it is commanded to run.
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- HCU
- ABS module
PINPOINT TEST R: DTCs C0020:15 AND C0020:71
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
NOTE: Failure to disconnect the battery when instructed results in false resistance readings. Refer to Battery, Mounting and Cables Battery Disconnect / Connect.
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R1 CHECK THE PUMP MOTOR (PMP_MOTOR) ACTIVE COMMAND
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: ABS Module DataLogger.
- Toggle the PMP_MOTOR active command ON.
- Listen for the ABS pump motor noise, does the ABS pump motor run for approximately 2 seconds?
Yes
GO to R2.
No
TOGGLE the PMP_MOTOR active command OFF. GO to R3.
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R2 CHECK FOR FAULT REPEATABILITY
- Drive the vehicle at speeds greater than 20 km/h (12 mph).
- Enter the following diagnostic mode on the scan tool: ABS Self-Test.
- Is DTCs C0020:15 or C0020:71 retrieved?
Yes
GO to R3.
No
The concern may have been caused by a loose or corroded connector. The system is operating correctly at this time.
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R3 CHECK THE ABS MODULE GROUND EYELET AT THE CHASSIS
- Ignition OFF.
- Remove the bolt retaining G135 on the LT frame rail.
- Clean the body mating surface and ground eyelets.
- Install the ground eyelet to the chassis with the retaining bolt.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: ABS Module Self-Test.
- Is DTCs C0020:15 or C0020:71 retrieved?
Yes
GO to R4.
No
The concern was caused by a loose or corroded connector. CLEAR the DTCs. REPEAT self-test.
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R4 CHECK THE PUMP MOTOR VOLTAGE SUPPLY TO THE ABS MODULE
- Ignition OFF.
- Disconnect: ABS Module C135.
- Measure the voltage between ABS module C135-1, circuit SBB96 (VT/RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to R5.
No
VERIFY that BJB fuse 96 (50A) is OK. If OK, REPAIR circuit SBB96 (VT/RD). If not OK, REFER to the Wiring Diagrams to identify the cause of the circuit short. CLEAR the DTCs and REPEAT the self-test. Diagrams By Number
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R5 CHECK THE ABS MODULE GROUND CIRCUITS FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between ABS module C135-13, circuit GD163 (BK/GY) harness side and ground; and between the ABS module C135-38, circuit GD163 (BK/GY), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to R6.
No
REPAIR circuit GD163 (BK/GY) for an open. CLEAR the DTCs. REPEAT the self-test.
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R6 CHECK FOR CORRECT ABS MODULE OPERATION
- Disconnect: ABS Module.
- Check for:
- corrosion
- pushed-out pins.
- spread terminals
- Connect: ABS Module.
- Make sure the connector is seated correctly, then operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new ABS module. REFER to Anti-Lock Brake System (ABS) Module Service and Repair. GO to R7.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.
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R7 CHECK FOR FAULT REPEATABILITY
- DRIVE the vehicle at speeds greater than 20 km/h (12 mph).
- Enter the following diagnostic mode on the scan tool: ABS Self-Test.
- Are DTCs C0020:15 or C0020:71 retrieved?
Yes
INSTALL a new HCU. REFER to Hydraulic Control Unit (HCU) Service and Repair. TEST the system for normal operation.
No
The repairs are complete. The system is operating correctly at this time.
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