Pinpoint Test J: The Brake Warning Indicator Is Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test J: The Brake Warning Indicator Is Always On
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 42, Vehicle Dynamic Systems for schematic and connector information. Diagrams By Number
Normal Operation
When the parking brake is applied, circuit CCB09 (GY/BU), to the Smart Junction Box (SJB), is grounded by the parking brake switch through circuit GD143 (BK/VT). The SJB receives the ground signal and sends the Instrument Cluster (IC) a message over the Medium Speed Controller Area Network (MS-CAN) to illuminate the brake warning indicator. The brake fluid level switch is hardwired to the ABS module through circuits CMC19 (GY/VT) and RMC19 (YE/GY). The brake fluid level switch is grounded through circuit GD120 (BK/GN). The ABS module monitors the brake fluid level and when the brake fluid level is low or a base brake system concern is detected, the ABS module sends a signal to the IC over the high High Speed Controller Area Network (HS-CAN) to illuminate the brake warning indicator.
NOTE: When the ABS module detects an Electronic Brake Distribution (EBD) fault, the ABS module sends a message to the IC. Whenever the IC receives an EBD message from the ABS module, the IC turns on both the brake warning indicator and the ABS warning indicator simultaneously.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Parking brake switch
- Brake fluid level switch (part of the master cylinder)
- SJB
- ABS module
- IC
PINPOINT TEST J: THE BRAKE WARNING INDICATOR IS ALWAYS ON
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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J1 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 lamp (BRK_LAMP) active command. 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 J2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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J2 CHECK THE SJB PARKING BRAKE INPUT
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Monitor the SJB parking brake PID (PRK_BRK) with the parking brake fully released.
- Does the PID indicate the parking brake is off?
Yes
GO to J5.
No
GO to J3.
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J3 CHECK THE PARKING BRAKE SWITCH
- Disconnect: Parking Brake Switch C2015.
- Observe the brake warning indicator.
- Does the brake warning indicator continue to illuminate?
Yes
GO to J4.
No
INSTALL a new parking brake switch. TEST the system for normal operation.
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J4 CHECK CIRCUIT CCB09 (GY/BU) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: SJB C2280b.
- Measure the resistance between the SJB C2280b-18, circuit CCB09 (GY/BU), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to J10.
No
REPAIR the circuit. TEST the system for normal operation.
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J5 CHECK THE ABS MODULE OPERATION
NOTE: Verify that the master cylinder reservoir is filled to the MAX line.
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Observe the brake warning indicator after the IC proves out.
- Connect a fused jumper wire between the brake fluid level switch C124-3, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-2, circuit RMC19 (YE/GY), harness side.
- Ignition ON.
- Does the brake warning indicator turn off?
Yes
REMOVE the jumper wire. INSTALL a new brake master cylinder. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to J6.
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J6 CHECK CIRCUIT CMC19 (GY/VT) FOR AN OPEN
- Ignition OFF.
- Disconnect: ABS Module C155.
- Measure the resistance between the ABS module C155-39, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-3, circuit CMC19 (GY/VT), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to J7.
No
REPAIR the circuit. TEST the system for normal operation.
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J7 CHECK CIRCUIT RMC19 (YE/GY) FOR AN OPEN
- Measure the resistance between the ABS module C155-7, circuit RMC19 (YE/GY), harness side and the brake fluid level switch C124-2, circuit RMC19 (YE/GY), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to J8.
No
REPAIR the circuit. TEST the system for normal operation.
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J8 CHECK CIRCUITS CMC19 (GY/VT) AND RMC19 (YE/GY) FOR A SHORT TO GROUND
- Measure the resistance between the ABS module C155-39, circuit CMC19 (GY/VT), harness side and ground; and between the ABS module C155-7, circuit RMC19 (YE/GY), harness side and ground.
- Are the resistances greater than 10,000 ohms?
Yes
GO to J9.
No
REPAIR the circuit in question. TEST the system for normal operation.
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J9 CHECK FOR CORRECT ABS MODULE OPERATION
- Disconnect the ABS module connector.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Correct the ABS module connector and make sure it seats correctly.
- Operate the system and verify that the concern is still present.
- Is the concern still present?
Yes
INSTALL a new ABS module. 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.
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J10 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. 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.
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