Pinpoint Test M: The Brake Warning Indicator Is Never On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test M: 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 brake warning indicator alerts the driver if any of the following brake system conditions are present: the parking brake is set, the brake fluid level is low or the ABS module detects an Electronic Brake Distribution (EBD) failure. If the brake system experiences an EBD failure, both the brake warning indicator and the ABS warning indicator illuminate.
When the parking brake is applied, the parking brake warning indicator switch grounds the parking brake input circuit to the Smart Junction Box (SJB). The SJB detects the ground signal and sends the IC a message over the Medium Speed Controller Area Network (MS-CAN) to illuminate the brake warning indicator.
The SJB provides a reference voltage to the brake fluid level switch on the input circuit. When the brake fluid level is low, the brake fluid level switch closes the input circuit to ground, pulling the reference low. When the SJB detects the reference voltage pulled low, the SJB sends a message to the IC over the MS-CAN to turn on the brake warning indicator.
When an EBD failure is detected, the ABS module sends a signal to the IC over the communication network to illuminate the brake system warning indicator.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Parking brake warning indicator switch
- Brake fluid level switch
- SJB
- IC
PINPOINT TEST M: 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.
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M1 CARRY OUT THE IC INDICATOR LAMP 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 and command the brake warning indicator on and off. Observe the brake warning indicator.
- Does the brake warning indicator illuminate when commanded on and turn off when commanded off?
Yes
GO to M2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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M2 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Monitor the SJB parking brake warning indicator switch PID (PRK_BRAKE) while applying the parking brake.
- Does the PID indicate ACTIVE with the parking brake applied?
Yes
GO to M6.
No
GO to M3.
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M3 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH
- Disconnect: Parking Brake Warning Indicator Switch C2015.
- Connect a fused jumper wire between the parking brake warning indicator switch C2015-1, circuit CLS05 (BU/GY), harness side and the parking brake warning indicator switch C2015-2, circuit GD126 (BK/WH), harness side.
- Does the brake warning indicator illuminate?
Yes
REMOVE the jumper wire. INSTALL a new parking brake warning indicator switch. REFER to Parking Brake System. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to M4.
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M4 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between the parking brake warning indicator switch C2015-2, circuit GD126 (BK/WH), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to M5.
No
REPAIR circuit GD126 (BK/WH) for an open. TEST the system for normal operation.
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M5 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH INPUT CIRCUIT FOR AN OPEN
- Disconnect: SJB C2280c.
- Measure the resistance between the SJB C2280c-1, circuit CLS05 (BU/GY), harness side and the parking brake warning indicator switch C2015-1, circuit CLS05 (BU/GY), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to M9.
No
REPAIR circuit CLS05 (BU/GY) for an open. TEST the system for normal operation.
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M6 CHECK THE SJB OPERATION USING THE SCAN TOOL
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Connect a fused jumper wire between the brake fluid level switch C124-2, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-1, circuit GD120 (BK/GN), harness side.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Monitor the brake fluid level PID (BRK_FLD_ST).
- Does the PID indicate LOW with the jumper wire in place?
Yes
REMOVE the jumper wire. GO to M8.
No
REMOVE the jumper wire. GO to M7.
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M7 CHECK THE 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 M8.
No
REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.
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M8 CHECK THE BRAKE FLUID LEVEL SWITCH PID USING THE SCAN TOOL
- Connect: Brake Fluid Level Switch C124.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Remove the brake fluid from the reservoir to allow the float to drop to the bottom of the reservoir.
- Monitor the SJB brake fluid PID (BRK_FLD_ST).
- Does the PID indicate LOW with the brake fluid level empty?
Yes
GO to M9.
No
INSTALL a new brake master cylinder. REFER to Hydraulic System, Brakes &/or Brake Pedal Assy. TEST the system for normal operation.
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M9 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 that the concern is still present.
- Is the concern still present?
Yes
INSTALL a new SJB. REFER to Body Control Systems. 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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