BAS Release Switch Circuit

BAS RELEASE SWITCH CIRCUIT





When Monitored and Set Condition
^ When Monitored: Ignition on.
^ Set Condition: The Controller Antilock Brake (CAB) detects a Brake Assist System (BAS) Release Switch malfunction.





For a complete Brake Assist System (BAS) Circuit Diagram refer to Diagrams; Electrical

Diagnostic Test
1. MEASURE THE VOLTAGE OF THE BAS RELEASE SWITCH SENSE (APPLIED) CIRCUIT
Turn the ignition off.
Disconnect the BAS Brake Booster harness connector.

Note: Check connectors - Clean/repair as necessary.

Turn the ignition on.





Measure the voltage of the BAS Release Switch Sense (Applied) circuit at the BAS Brake Booster harness connector.
Is the voltage above 5.0 volts?
Yes >> Repair the BAS Release Switch Sense (Applied) circuit for a short to voltage. Perform ABS VERIFICATION TEST. ABS Verification Test
No >> Go to 2

2. MEASURE THE RESISTANCE BETWEEN THE BAS RELEASE SWITCH SENSE (APPLIED) CIRCUIT AND THE SENSE (REFERENCE) CIRCUIT
With the ignition off.
Disconnect the CAB harness connector.

Note: Check connectors - Clean/repair as necessary.





Measure the resistance between the BAS Release Switch Sense (Applied) circuit and the Sense (Reference) circuit in the BAS Brake Booster harness connector.
Is the resistance below 5.0 ohms?
Yes >> Repair the BAS Release Switch Sense (Applied) circuit for a short to the Sense (Reference) circuit. Perform ABS VERIFICATION TEST.
No >> Go to 3

3. MEASURE THE RESISTANCE OF THE BAS RELEASE SWITCH SENSE (APPLIED) CIRCUIT
With the ignition off.





Measure the resistance of the BAS Release Switch Sense (Applied) circuit from the CAB harness connector to the BAS Brake Booster harness connector.
Is the resistance below 5.0 ohms?
Yes >> Go to 4
No >> Repair the BAS Release Switch Sense (Applied) circuit for an open. Perform ABS VERIFICATION TEST.

4. MEASURE THE RESISTANCE BETWEEN GROUND AND THE BAS RELEASE SWITCH 12 VOLT SUPPLY CIRCUIT
With the ignition off.





Measure the resistance between ground and the BAS Release Switch 12 Volt Supply circuit.
Is the resistance below 100 ohms?
Yes >> Repair the BAS Release Switch 12 Volt Supply circuit for a short to ground. Perform ABS VERIFICATION TEST.
No >> Go to 5

5. MEASURE THE VOLTAGE OF THE SENSE (REFERENCE) CIRCUIT
With the ignition off.
Reconnect the CAB harness connector.
Turn the ignition on.





Measure the voltage of the BAS Release Switch Sense (Reference) circuit at the BAS Brake Booster harness connector.
Is the voltage between 10 and 12 volts?
Yes >> Go to 6
No >> Go to 8

6. MEASURE THE RESISTANCE BETWEEN GROUND AND THE BAS RELEASE SWITCH SENSE (APPLIED) CIRCUIT
Turn the ignition off.
Disconnect the CAB harness connector.

Note: Check connectors - Clean/repair as necessary.





Measure the resistance between ground and the BAS Release Switch Sense (Applied) circuit.
Is the resistance below 100 ohms?
Yes >> Repair the BAS Release Switch Sense (Applied) circuit for a short to ground. Perform ABS VERIFICATION TEST.
No >> Go to 7

7. MEASURE THE RESISTANCE BETWEEN THE BAS RELEASE SWITCH SENSE (APPLIED) CIRCUIT AND THE 12 VOLT SUPPLY CIRCUIT
With the ignition off.





Measure the resistance between the BAS Release Switch Sense (Applied) circuit and the BAS Release Switch 12 Volt Supply circuit in the BAS Brake Booster harness connector.
Is the resistance below 100 ohms?
Yes >> Repair the BAS Release Switch Sense (Applied) circuit for a short to the BAS Release Switch 12 Volt Supply circuit. Perform ABS VERIFICATION TEST.
No >> Replace the BAS Brake Booster. Perform ABS VERIFICATION TEST.

8. MEASURE THE RESISTANCE BETWEEN GROUND AND THE BAS RELEASE SWITCH SENSOR (RELEASED) CIRCUIT
Turn the ignition off.
Disconnect the CAB harness connector.

Note: Check connectors - Clean/repair as necessary.





Measure the resistance between ground and the BAS Release Switch Sensor (Released) circuit at the BAS Brake Booster harness connector.
Is the resistance below 100 ohms?
Yes >> Repair the BAS Release Switch Sensor (Released) circuit for a short to ground. Perform ABS VERIFICATION TEST.
No >> Go to 9

9. MEASURE THE RESISTANCE OF THE BAS RELEASE SWITCH SENSE (RELEASED) CIRCUIT
With the ignition off.





Measure the resistance of the BAS Release Switch Sensor (Released) circuit at the BAS Brake Booster harness connector and the CAB harness connector.
Is the resistance below 5.0 ohms?
Yes >> Replace the Controller Antilock Brake. Perform ABS VERIFICATION TEST.
No >> Repair the BAS Release Switch Sensor (Released) circuit for an open. Perform ABS VERIFICATION TEST.