78 - Foundation Brake

FOUNDATION BRAKE-78





For a complete wiring diagram, refer to Wiring Diagram Information.

When Monitored
With the ignition on and no system under voltage DTC present.

Set Condition
Low feedback voltage from the Brake Fluid Level Switch Sense circuit.

Possible Causes
- INTERMITTENT BRAKE FLUID LEVEL LOW DTC
- BRAKE FLUID LEVEL LOW
- BRAKE FLUID LEVEL SWITCH SENSE CIRCUIT SHORT TO GROUND
- GROUND CIRCUIT OPEN OR HIGH RESISTANCE
- BRAKE FLUID LEVEL SENSOR
- CONTROLLER ANTI-LOCK BRAKE

Diagnostic Test
1. DTC CONDITION IS PRESENT
Release the Parking Brake.
Turn the ignition off.
Turn the ignition on.
Monitor the Instrument Cluster.

Does the red Brake Warning Indicator stay on?
Yes >> Go To 2
No >> Go To 6

2. BRAKE FLUID LEVEL LOW
Turn the ignition off.
Inspect the Brake Fluid Level in accordance with the Service Information.

Is the Brake Fluid Level Low?
Yes >> Inspect the system and repair as necessary in accordance with the Service Information.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test
No >> Go To 3

3. BRAKE FLUID LEVEL SWITCH SENSE CIRCUIT SHORT TO GROUND





Turn the ignition off.
Disconnect the Brake Fluid Level Sensor harness connector.
Disconnect the CAB harness connector.

NOTE: Check connector - Clean/repair as necessary. Measure the resistance between ground and the Brake Fluid Level Switch Sense circuit.

Is the resistance below 5.0 ohms?
Yes >> Repair the Brake Fluid Level Switch Sense circuit for a short to ground.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test
No >> Go To 4

4. BRAKE FLUID LEVEL SENSOR

NOTE: Determine if the Brake Fluid Level Sensor is stuck in the down position. Repair as necessary.

Measure the resistance of the Brake Fluid Level Sensor at the sensor terminals.

NOTE: Resistance should be approximately 10,000 ohms with the reservoir full.

Is the resistance between 9,500 and 10,500 ohms?
Yes >> Go To 5
No >> Replace the Brake Fluid Level Switch in accordance with the Service Information.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test

5. GROUND CIRCUIT OPEN OR HIGH RESISTANCE





Using a 12-volt test light connected to 12 volts, check the Ground circuit.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?
Yes >> Replace the Controller Anti-lock Brake in accordance with the Service Information. Refer to the symptom *Replacing the Controller Anti-lock Brake.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test
No >> Repair the Brake Fluid Level Switch ground circuit for an open circuit or high resistance.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test

6. WIRING HARNESS INSPECTION
Turn the ignition off.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.
Visually inspect the related wire harness connectors. Look for broken, bent, pushed out, or corroded terminals.

Refer to any Technical Service Bulletins that may apply.

Were any problems found?
Yes >> Repair as necessary.
Perform ABS VERIFICATION TEST - VER 1. ABS Verification Test
No >> Test Complete.