1000 - 1999: 1202

1202 - BAS RELEASE SWITCH PLAUSIBILITY ERROR





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 Antilock Brake System (ABS) Circuit Diagram Brakes - ABS Electrical Diagnostics.

Diagnostic Test

1. MEASURE THE VOLTAGE OF THE BAS RELEASE SWITCH SENSOR (APPLIED) CIRCUIT




Turn the ignition off.
Disconnect the BAS Brake Booster C2 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Turn the ignition on.
Measure the voltage of the BAS Release Switch Sensor (Applied) circuit at the BAS Brake Booster C2 harness connector.
Is the voltage below 1.0 volt?

Yes

- Go to 4

No

- Go to 2

2. MEASURE THE VOLTAGE OF THE SENSOR (APPLIED) CIRCUIT




Turn the ignition off.
Disconnect the CAB harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Turn the ignition on.
Measure the voltage of the BAS Release Switch Sensor (Applied) circuit at the BAS Brake Booster C2 harness connector.
Is the voltage below 1.0 volt?

Yes

- Go to 3

No

- Repair the BAS Release Switch Sensor (Applied) circuit for a short to voltage.
- Perform ABS VERIFICATION TEST. ABS Verification Test

3. MEASURE THE RESISTANCE BETWEEN THE BAS RELEASE SWITCH SENSOR (APPLIED) CIRCUIT AND ALL OTHER CAB VOLTAGE CIRCUITS




Turn the ignition off.
Measure the resistance between the BAS Release Switch Sensor (Applied) circuit and the Sensor (Released) circuit in the BAS Brake Booster C2 harness connector.
Measure the resistance between the BAS Release Switch Sensor (Applied) circuit and all 5 and 12 volt circuits in the CAB harness connector.
Is the resistance for all measurements above 100k ohms?

Yes

- Replace the Controller Antilock Brake (CAB) Module. Removal.
- Perform ABS VERIFICATION TEST. ABS Verification Test

No

- Repair the BAS Release Switch Sensor (Applied) circuit for a short to the circuit(s) that measured less than 100k ohms.
- Perform ABS VERIFICATION TEST. ABS Verification Test

4. MEASURE THE VOLTAGE OF THE BAS RELEASE SWITCH 12 VOLT SUPPLY CIRCUIT




With the ignition on.
Measure the voltage of the BAS Release Switch 12 Volt Supply circuit at the BAS Brake Booster C2 harness connector.
Is the voltage above 10 volts?

Yes

- Go to 5

No

- Go to 6

5. MEASURE THE VOLTAGE OF THE BAS RELEASE SWITCH SENSOR (RELEASED) CIRCUIT




With the ignition on.
Measure the voltage of the BAS Release Switch Sensor (Released) circuit at the BAS Brake Booster C2 harness connector.
Is the voltage above 10 volts?

Yes

- Go to 10

No

- Go to 8

6. MEASURE THE RESISTANCE BETWEEN GROUND AND THE 12 VOLT SUPPLY 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 12 Volt Supply circuit at the BAS Brake Booster C2 harness connector.
Is the resistance above 100k ohms?

Yes

- Go to 7

No

- Repair the BAS Release Switch 12 Volt Supply circuit for a short to ground.
- Perform ABS VERIFICATION TEST. ABS Verification Test

7. MEASURE THE RESISTANCE OF THE 12 VOLT SUPPLY CIRCUIT




With the ignition off.
Measure the resistance of the BAS Release Switch 12 Volt Supply circuit from the BAS Brake Booster C2 harness connector to the CAB harness connector.
Is the resistance below 5.0 ohms?

Yes

- Replace the Controller Antilock Brake (CAB) Module. Removal.
- Perform ABS VERIFICATION TEST. ABS Verification Test

No

- Repair the BAS Release Switch 12 Volt Supply circuit for an open.
- Perform ABS VERIFICATION TEST. 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 C2 harness connector.
Is the resistance above 100k ohms?

Yes

- Go to 9

No

- Repair the BAS Release Switch Sensor (Released) circuit for a short to ground.
- Perform ABS VERIFICATION TEST. ABS Verification Test

9. MEASURE THE RESISTANCE OF THE BAS RELEASE SWITCH SENSOR (RELEASED) CIRCUIT




With the ignition off.
Measure the resistance of the BAS Release Switch Sensor (Released) circuit from the BAS Brake Booster C2 harness connector to the CAB harness connector.
Is the resistance below 5.0 ohms?

Yes

- Replace the Controller Antilock Brake (CAB) Module. Removal
- Perform ABS VERIFICATION TEST. ABS Verification Test

No

- Repair the BAS Release Switch Sensor (Released) circuit for an open.
- Perform ABS VERIFICATION TEST. ABS Verification Test

10. MEASURE THE RESISTANCE BETWEEN GROUND AND THE BAS RELEASE SWITCH SENSOR (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 Sensor (Applied) circuit at the BAS Brake Booster C2 harness connector.
Is the resistance above 100k ohms?

Yes

- Go to 11

No

- Repair the BAS Release Switch Sensor (Applied) circuit for a short to ground.
- Perform ABS VERIFICATION TEST. ABS Verification Test

11. MEASURE THE RESISTANCE OF THE BAS RELEASE SWITCH SENSOR (APPLIED) CIRCUIT




With the ignition off.
Measure the resistance of the BAS Release Switch Sensor (Applied) circuit from the BAS Brake Booster C2 harness connector to the CAB harness connector.
Is the resistance below 5.0 ohms?

Yes

- Go to 12

No

- Repair the BAS Release Switch Sensor (Applied) circuit for an open.
- Perform ABS VERIFICATION TEST. ABS Verification Test

12. MEASURE THE RESISTANCE BETWEEN GROUND AND THE BAS RELEASE SWITCH SENSOR (APPLIED) CIRCUIT WITH CAB CONNECTED




With the ignition off.
Reconnect the CAB harness connector.
Measure the resistance between ground and the BAS Release Switch Sensor (Applied) circuit at the BAS Brake Booster C2 harness connector.
Is the resistance 6.5-7.0k ohms?

Yes

- Replace the BAS Release Switch (Brake Booster). Power Brake Booster - Removal
- Perform ABS VERIFICATION TEST. ABS Verification Test

No

- Replace the Controller Antilock Brake (CAB) Module. Removal
- Perform ABS VERIFICATION TEST. ABS Verification Test