Pinpoint Test M: The Brake Warning Indicator Is Never On
Instrumentation 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 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.
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 cap)
- 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 if false resistance readings. Refer to Battery, Mounting and Cables Battery Disconnect.
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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 on and off. Observe the BRAKE warning indicator.
- Does the BRAKE warning indicator illuminate when selected on, and turn off when selected off?
Yes
GO to M2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Service and Repair. TEST the system for normal operation.
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M2 CHECK THE PARKING BRAKE SWITCH INPUT
- Apply the parking brake.
- Does the BRAKE warning indicator illuminate?
Yes
GO to M3.
No
GO to M4.
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M3 CHECK THE BRAKE FLUID LEVEL SWITCH GROUND CIRCUIT FOR AN OPEN
NOTE: Verify that the brake fluid is low or was low at the time the concern was identified before continuing with this test step.
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: Brake Fluid Level Switch C124.
- Measure the resistance between the brake fluid level switch C124-3, circuit 91-GC7 (BK/BU), harness side and ground.
- Is the resistance less then 5 ohms?
Yes
INSTALL a new brake fluid level switch (brake fluid reservoir cap). TEST the system for normal operation.
No
REPAIR circuit 91-GC7 (BK/BU) for an open. TEST the system for normal operation.
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M4 CHECK THE PARKING BRAKE SWITCH
- Ignition OFF.
- Disconnect: Parking Brake Warning Indicator Switch C306.
- Connect a fused jumper wire between the parking brake warning indicator switch C306-1, circuit 31S-GE44 (BK/RD), harness side and ground.
- Ignition ON.
- Monitor the brake warning indicator.
- Does the brake warning indicator turn on?
Yes
INSTALL a new parking brake warning indicator switch. TEST the system for normal operation.
No
GO to M5.
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M5 CHECK THE BRAKE WARNING INPUT CIRCUIT TO THE PARKING BRAKE WARNING INDICATOR SWITCH FOR AN OPEN
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Measure the resistance between the parking brake warning indicator switch C306-1, circuit 31S-GE44 (BK/RD), harness side and the brake fluid level switch C124-1, circuit 31S-GE44 (BK/RD), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to M6.
No
REPAIR circuit 31S-GE44 (BK/RD) for an open. TEST the system for normal operation.
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M6 CHECK THE BRAKE FLUID LEVEL SWITCH
- Measure the resistance between the brake fluid level switch, pin 1, component side and the brake fluid level switch, pin 2, component side.
- Is the resistance less than 5 ohms?
Yes
GO to M7.
No
INSTALL a new brake fluid level switch (brake fluid level reservoir cap). TEST the system for normal operation.
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M7 CHECK THE BRAKE WARNING INPUT CIRCUIT FOR AN OPEN BETWEEN THE IC AND THE BRAKE FLUID LEVEL SWITCH
- Disconnect: IC C220b.
- Measure the resistance between the IC C220b-7, circuit 31S-GC6 (BK/YE), harness side and the brake fluid level switch C124-2, circuit 31S-GC6 (BK/YE) harness side.
- Is the resistance less than 5 ohms?
Yes
GO to M8.
No
REPAIR circuit 31S-GC6 (BK/YE) for an open. TEST the system for normal operation.
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M8 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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