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
Normal Operation
When the parking brake is applied, the parking brake warning indicator switch grounds circuit CCB09 (GY/BU) to the Smart Junction Box (SJB). The SJB receives the ground signal and sends the Instrument Cluster (IC) a message over the communication network to illuminate the brake warning indicator. When the brake fluid level is low, the brake fluid level switch closes, and the signal from the SJB on circuit CMC19 (GY/VT) is grounded on circuit GD121 (BK/YE). When a base brake system concern 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 (part of the brake fluid reservoir)
- 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 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. 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 BRAKE WARNING INDICATOR WITH THE PARKING BRAKE APPLIED
- Apply the parking brake while monitoring the brake warning indicator.
- Does the brake warning indicator illuminate?
Yes
GO to I6.
No
GO to I3.
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I3 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH PID
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Monitor the SJB parking brake warning indicator switch PID (PRK_BRK) while applying the parking brake.
- Does the PID agree with the parking brake position?
Yes
GO to I9.
No
GO to I4.
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I4 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH
- Disconnect: Parking Brake Warning Indicator Switch C306.
- Connect a fused jumper wire between the parking brake warning indicator switch C306-1, circuit CCB09 (GY/BU), harness side and ground.
- Does the brake warning indicator illuminate?
Yes
REMOVE the jumper wire. INSTALL a new parking brake warning indicator switch. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to I5.
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I5 CHECK CIRCUIT CCB09 (GY/BU) FOR AN OPEN
- Ignition OFF.
- Disconnect: SJB C2280c.
- Measure the resistance between the SJB C2280c-9, circuit CCB09 (GY/BU), harness side and the parking brake warning indicator switch C306-1, 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 BRAKE FLUID LEVEL WARNING INDICATOR OPERATION FROM THE BRAKE FLUID LEVEL SWITCH
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Ignition ON.
- Connect a fused jumper wire between the brake fluid level switch C124-1, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-2, circuit GD121 (BK/YE), harness side.
- Monitor the brake warning indicator.
- Does the brake warning indicator illuminate?
Yes
REMOVE the jumper wire. INSTALL a new brake fluid reservoir. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to I7.
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I7 CHECK CIRCUIT GD121 (BK/YE) FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between the brake fluid level switch C124-2, circuit GD121 (BK/YE), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to I8.
No
REPAIR the circuit. TEST the system for normal operation.
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I8 CHECK CIRCUIT CMC19 (GY/VT) FOR AN OPEN
- Disconnect: SJB C2280a.
- Measure the resistance between the SJB C2280a-25, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-1, circuit CMC19 (GY/VT), 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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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 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.
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