No Response From Controller Antilock Brake

POSSIBLE CAUSES
- Fused B+ circuit(s) open
- Traction system relay output circuit open
- Ground circuit(s) open
- SCI transmit circuit open
- SCI transmit circuit shorted to ground
- SCI transmit circuit shorted to voltage
- Controller antilock brake module

Diagnostic Test




1. FUSED B+ CIRCUIT(S) OPEN

Turn the ignition off.
Disconnect the CAB harness connector.

NOTE: Check connector Clean/repair as necessary.

Turn the ignition on.
Measure the voltage of the Fused B+ circuits at the CAB harness connector.

Q: Is the voltage above 10 volts?

YES: Go to 2
NO: Repair the Fused B+ circuit(s) for an open. Perform ABS VERIFICATION TEST.




2. TRACTION SYSTEM RELAY OUTPUT CIRCUIT OPEN

With the ignition on.
Measure the voltage of the Traction System Relay Output circuit at the CAB harness connector.

Q: Is the voltage above 10 volts?

YES: Go to 3
NO: Repair the Traction System Relay Output circuit for an open. Perform ABS VERIFICATION TEST.




3. GROUND CIRCUIT(S) OPEN

Turn the ignition off.
Measure the resistance of the Ground circuits from the CAB harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Go to 4
NO: Repair the Ground circuit(s) for an open. Perform ABS VERIFICATION TEST.




4. SCI TRANSMIT CIRCUIT OPEN

With the ignition off.
Measure the resistance of the SCI Transmit circuit from the CAB harness connector to the DLC.

Q: Is the resistance below 5.0 ohms?

YES: Go to 5
NO: Repair the SCI Transmit circuit for an open. Perform ABS VERIFICATION TEST.




5. SCI TRANSMIT CIRCUIT SHORTED TO GROUND

With the ignition off. Measure the resistance between ground and the SCI Transmit circuit.

Q: Is the resistance below 100 kohms?

YES: Repair the SCI Transmit circuit for a short to ground. Perform ABS VERIFICATION TEST.
NO: Go to 6




6. SCI TRANSMIT CIRCUIT SHORTED TO VOLTAGE

Turn the ignition on.
Measure the voltage of the SCI Transmit circuit at the CAB.

Q: Is the voltage above 0.5 volt?

YES: Repair the SCI Transmit circuit for a short to voltage. Perform ABS VERIFICATION TEST.
NO: Replace the Controller Antilock Brake Module.Perform ABS VERIFICATION TEST.