Pinpoint Test N: The Brake Warning Indicator Is Always On
Instrumentation and Warning Chimes
Pinpoint Tests
Pinpoint Test N: The Brake Warning Indicator is Always On
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information. Diagrams By Number
Normal Operation
The Instrument Cluster (IC) uses 3 basic inputs to control the brake warning indicator. The first 2 are the parking brake warning indicator switch and the brake fluid level switch. The third is for the Electronic Brake Distribution (EBD), controlled by the ABS. The parking brake warning indicator switch is hardwired through the brake fluid level switch and the brake warning input circuit to the IC. The EBD input is a message sent from the ABS module over the High Speed Controller Area Network (HS-CAN) communication bus.
The IC provides a reference voltage on the brake warning input circuit. When the parking brake is applied, the parking brake warning indicator switch closes, supplying ground through the brake fluid level switch on the brake warning input circuit, pulling the reference voltage low to the IC. When a low brake fluid level condition exists, the brake fluid level switch closes to ground pulling the brake warning input circuit low to the IC. The IC monitors the brake warning input circuit and when the voltage is pulled low, the IC turns on the brake warning indicator. When the ABS module detects a base brake system concern, other ABS related or EBD concerns, the ABS module sends a message to the IC to illuminate both the ABS warning indicator and the brake warning indicator.
NOTE: Both the ABS warning indicator and the brake warning indicator illuminate if the input to turn on the brake warning indicator is received from the ABS module.
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)
- ABS concern
- IC
PINPOINT TEST N: 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.
NOTE: Verify that the brake fluid level is full and the parking brake is fully released before proceeding with the diagnostics.
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N1 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 and off. Observe the brake warning indicator.
- Does the brake warning indicator turn off when commanded off?
Yes
GO to N2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Service and Repair. TEST the system for normal operation.
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N2 RETRIEVE THE RECORDED DTCs FROM THE ABS MODULE SELF-TEST
- Check for recorded ABS module DTCs from the self-test.
- Are any DTCs recorded?
Yes
REFER to Antilock Brakes / Traction Control Systems.
No
GO to N3.
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N3 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH
- Ignition OFF.
- Disconnect: Parking Brake Warning Indicator Switch C306.
- Ignition ON.
- Monitor the brake warning indicator.
- Does the brake warning indicator turn off?
Yes
INSTALL a new parking brake warning indicator switch. TEST the system for normal operation.
No
GO to N4.
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N4 CHECK THE BRAKE FLUID LEVEL SWITCH
NOTE: Verify that the brake fluid reservoir is full before proceeding with this pinpoint test step.
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Ignition ON.
- Does the brake warning indicator turn off?
Yes
GO to N5.
No
GO to N6.
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N5 CHECK THE BRAKE WARNING INPUT CIRCUIT TO THE PARKING BRAKE WARNING INDICATOR SWITCH FOR A SHORT TO GROUND
- Measure the resistance between the parking brake warning indicator switch C306-1, circuit 31S-GE44 (BK/RD), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
INSTALL a new brake fluid level switch (brake fluid reservoir cap). TEST the system for normal operation.
No
REPAIR circuit 31S-GE44 (BK/RD) for a short to ground. TEST the system for normal operation.
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N6 CHECK THE BRAKE WARNING INPUT CIRCUIT TO THE INSTRUMENT CLUSTER FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: IC C220b.
- Measure the resistance between the IC C220b-7, circuit 31S-GC6 (BK/YE), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to N7.
No
REPAIR circuit 31S-GC6 (BK/YE) for a short to ground. CLEAR the DTCs. REPEAT the self-test.
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N7 CHECK FOR CORRECT IC OPERATION
- Disconnect the IC connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the IC 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 IC. REFER to Instrument Cluster (IC) 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.
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