Pinpoint Test I: The Brake Warning Indicator Is Never On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test I: The Brake Warning Indicator Is Never 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 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)
- ABS module
- SJB
- IC
PINPOINT TEST I: 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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I1 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). Command the brake warning indicator on. Observe the brake warning indicator.
- Does the brake warning indicator illuminate when commanded on?
Yes
GO to I2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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I2 CHECK THE PARKING BRAKE SWITCH PID
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Select the SJB parking brake switch PID (PRK_BRK) while applying the parking brake.
- Does the PID agree with the parking brake position?
Yes
GO to I6.
No
GO to I3.
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I3 CHECK THE PARKING BRAKE SWITCH
- Ignition OFF.
- Disconnect: Parking Brake Switch C2015.
- Ignition ON.
- Connect a fused jumper wire between the parking brake switch C2015-1, circuit GD143 (BK/VT), harness side and the parking brake switch C2015-2, circuit CCB09 (GY/BU), harness side.
- Does the brake warning indicator illuminate?
Yes
INSTALL a new parking brake switch. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to I4.
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I4 CHECK CIRCUIT GD143 (BK/VT) FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the parking brake switch C2015-1, circuit GD143 (BK/VT), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to I5.
No
REPAIR the circuit. TEST the system for normal operation.
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I5 CHECK CIRCUIT CCB09 (GY/BU) FOR AN OPEN
- Disconnect: SJB C2280b.
- Measure the resistance between the SJB C2280b-18, circuit CCB09 (GY/BU), harness side and the parking brake switch C2015-2, circuit CCB09 (GY/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to I9.
No
REPAIR the circuit. TEST the system for normal operation.
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I6 CHECK THE ABS MODULE OPERATION
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Ignition ON.
- Observe the brake warning indicator after the IC proves out.
- Does the brake warning indicator illuminate with the brake fluid level switch disconnected?
Yes
REMOVE the jumper wire. GO to I7.
No
REMOVE the jumper wire. GO to I8.
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I7 CHECK CIRCUIT GD120 (BK/GN) FOR AN OPEN
- 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
INSTALL a new brake master cylinder. TEST the system for normal operation.
No
REPAIR the circuit. TEST the system for normal operation.
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I8 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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I9 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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