Pinpoint Test O: The Brake Warning Indicator Is Never On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test O: The Brake Warning Indicator Is Never On
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information. Diagrams By Number
Normal Operation
The IC uses 3 basic messaged inputs to control the brake warning indicator. The first 2 are the parking brake switch and brake fluid level switch. The third is for the Electronic Brake Distribution (EBD), controlled by the ABS. The parking brake switch and the brake fluid level switch status are sent from the Smart Junction Box (SJB) over the Medium Speed Controller Area Network (MS-CAN) communication bus. The EBD message is sent from the ABS module over the High Speed Controller Area Network (HS-CAN) communication bus lines. The parking brake switch is hardwired to the SJB through the parking brake input circuit. The brake fluid level switch is hardwired to the SJB through the brake fluid level signal circuit and return circuit. When the parking brake is applied, the parking brake switch closes to ground through the ground circuit, providing a ground to the SJB and pulling the parking brake input circuit low. When a low brake fluid level condition exists, the low brake fluid level switch closes to ground, pulling the brake fluid level circuit low. The SJB monitors the parking brake and low brake fluid level inputs and sends the IC a message to turn on the brake warning indicator when the parking brake is applied or the brake fluid is low. When the ABS module detects a base brake system concern or other ABS related concerns that affect the EBD function, the ABS module sends a message to the IC to illuminate both the ABS warning indicator and the brake warning indicator.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Brake fluid level switch (part of the master cylinder)
- Brake fluid level switch
- SJB
- IC
PINPOINT TEST O: THE BRAKE WARNING INDICATOR IS NEVER ON
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 will result in false resistance readings. Refer to Battery, Mounting and Cables Battery Disconnect.
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O1 CARRY OUT THE IC INDICATOR LAMP CONTROL ACTIVE COMMAND USING THE SCAN TOOL
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IC DataLogger .
- Select the IC brake warning indicator (BRK_LAMP) active command on. Observe the brake warning indicator.
- Does the brake warning indicator illuminate when commanded on?
Yes
GO to O2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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O2 CHECK THE PARKING BRAKE SWITCH PID
- Enter the following diagnostic mode on the scan tool: SJB DataLogger .
- Monitor the SJB (PRK_BRAKE) PID while applying the parking brake.
- Does the PID agree with the parking brake position?
Yes
GO to O6.
No
GO to O3.
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O3 CHECK THE PARKING BRAKE SWITCH
- Disconnect: Parking Brake Switch C2015 .
- Connect a fused jumper wire between the parking brake switch C2015-2, circuit GD143 (BK/VT), harness side and the parking brake switch C2015-1, circuit CCB01 (VT/BN), harness side.
- Does the brake warning indicator illuminate?
Yes
REMOVE the jumper wire. INSTALL a new parking brake switch. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to O4.
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O4 CHECK THE PARKING BRAKE SWITCH GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable .
- Measure the resistance between the parking brake switch C2015-2, circuit GD143 (BK/VT), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to O5.
No
REPAIR circuit GD143 (BK/VT) for an open. TEST the system for normal operation.
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O5 CHECK THE PARKING BRAKE INPUT CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: SJB C2280C .
- Measure the resistance between the SJB C2280c-1, circuit CCB01 (VT/BN), harness side and the parking brake switch C2015-1, circuit CCB01 (VT/BN), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to O9.
No
REPAIR circuit CCB01 (VT/BN) for an open. TEST the system for normal operation.
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O6 CHECK THE BRAKE FLUID LEVEL SWITCH OPERATION
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124 .
- Ignition ON.
- Does the brake warning indicator illuminate?
Yes
GO to O7.
No
GO to O9.
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O7 CHECK BRAKE FLUID LEVEL SWITCH GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable .
- Measure the resistance between the brake fluid level switch C124-1, circuit GD120 (BK/GN), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to O8.
No
REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.
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O8 CHECK THE BRAKE FLUID LEVEL SWITCH
- Ignition ON.
- NOTICE: Do not spill brake fluid onto painted or plastic surfaces. If spilled, wipe up immediately before damage to the painted or plastic surface occurs.
- Remove the brake fluid from the reservoir to allow the brake fluid level switch to fall to the bottom of the reservoir.
- Measure the resistance between the brake fluid level switch C124 pin 3, component side and the brake fluid level switch C124 pin 1, component side.
- Is the resistance less than 5 ohms?
Yes
GO to O9.
No
INSTALL a new master cylinder. REFER to Hydraulic Brake Actuation Service and Repair. TEST the system for normal operation.
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O9 CHECK FOR CORRECT SJB OPERATION
- Disconnect all the SJB connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new SJB. REFER to Multifunction Electronic Modules Service and Repair. TEST the system for normal operation.
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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