Pinpoint Test N: The Brake Warning Indicator Is Never On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test N: 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 messaged inputs to control the brake warning indicator. The first 2 are the parking brake warning indicator switch and brake fluid level switch. The third is for the Electronic Brake Distribution (EBD), controlled by the ABS. The parking brake warning indicator switch and the brake fluid level switch status are sent from the Smart Junction Box (SJB) over the Medium Speed Controller Area Network (MS-CAN) communication bus. The EBD message is sent from the ABS module over the High Speed Controller Area Network (HS-CAN) communication bus lines. The parking brake warning indicator switch is hardwired to the SJB through circuit CMC25 (WH/VT). The brake fluid level switch is hardwired to the SJB through signal circuit CMC19 (GY/VT) and return circuit RMC19 (YE/GY).
The SJB provides a reference voltage to both the parking brake warning indicator switch and the brake fluid level switch. When the parking brake is applied, the parking brake warning indicator switch closes to ground through circuit GD133 (BK), providing a ground to the SJB and pulling signal circuit CMC25 (WH/VT) low. When a low brake fluid level condition exists, the low brake fluid level switch closes to ground through circuit GD120 (BK/GN), pulling signal circuit CMC19 (GY/VT) low. The SJB monitors the parking brake and the brake fluid level inputs sending the IC a message to turn the brake warning indicator on when the parking brake is applied, when the brake fluid level is low or if the SJB detects an open in the brake fluid level signal or return circuits. When the ABS module detects a base brake system concern or other ABS related concerns that affect the EBD function, 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 master cylinder)
- SJB
- IC
PINPOINT TEST N: 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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N1 RETRIEVE THE RECORDED DTCs FROM BOTH THE CONTINUOUS AND ON-DEMAND IC SELF-TESTS
- Check for recorded IC DTCs from the continuous self-test.
- Are any DTCs recorded?
Yes
For DTC U2472, Go To Pinpoint Test AD. Pinpoint Tests AD: DTC B2A20 Or U2472
For all other DTCs, REFER to DTC Charts. Instrumentation, Message Center and Warning Chimes
No
GO to N2.
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N2 DETERMINE IF THE BRAKE WARNING INDICATOR OPERATES WITH THE PARKING BRAKE
- Ignition ON.
- Apply the parking brake while monitoring the brake warning indicator.
- Does the brake warning indicator illuminate with the parking brake applied?
Yes
GO to N8.
No
GO to N3.
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N3 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 observe the brake warning indicator.
- Does the brake warning indicator illuminate when commanded on?
Yes
GO to N4.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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N4 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH PID
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Select the SJB parking brake PID (PRK_BRAKE). Monitor the parking brake PID while applying the parking brake.
- Does the PID agree with the parking brake position?
Yes
GO to N12.
No
GO to N5.
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N5 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 C306-2, circuit GD133 (BK), harness side and the parking brake warning indicator switch C306-1, circuit CMC25 (WH/VT), harness side.
- 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 N6.
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N6 CHECK CIRCUIT GD133 (BK) FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Ignition OFF.
- Measure the resistance between the parking brake warning indicator switch C306-2, circuit GD133 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to N7.
No
REPAIR the circuit. TEST the system for normal operation.
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N7 CHECK CIRCUIT CMC25 (WH/VT) FOR AN OPEN
- Disconnect: SJB C2280c.
- Measure the resistance between the SJB C2280c-1, circuit CMC25 (WH/VT), harness side and the parking brake warning indicator switch C306-1, circuit CMC25 (WH/VT), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to N12.
No
REPAIR the circuit. TEST the system for normal operation.
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N8 CHECK THE BRAKE FLUID LEVEL SWITCH OPERATION
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Ignition ON.
- Does the brake warning indicator illuminate?
Yes
GO to N10.
No
GO to N9.
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N9 CHECK CIRCUITS CMC19 (GY/VT) AND RMC19 (YE/GY) FOR A SHORT TOGETHER
- Ignition OFF.
- Disconnect: SJB C2280f.
- Measure the resistance between the brake fluid level switch C124-2, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-3, circuit RMC19 (YE/GY), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to N12.
No
REPAIR the circuits. TEST the system for normal operation.
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N10 CHECK CIRCUIT GD120 (BK/GN) FOR AN OPEN
- Ignition OFF.
- 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
GO to N11.
No
REPAIR the circuit. TEST the system for normal operation.
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N11 CHECK THE BRAKE FLUID LEVEL SWITCH
- Ignition ON.
- NOTICE: Do not spill brake fluid onto painted or plastic surfaces. If spilled, wipe up immediately before damage to the painted or plastic surface occurs.
- Remove the brake fluid from the reservoir to allow the brake fluid level switch to fall to the bottom of the reservoir.
- Measure the resistance between the brake fluid level switch C124 pin 3, component side and the brake fluid level switch C124 pin 1, component side.
- Is the resistance less than 5 ohms?
Yes
GO to N12.
No
INSTALL a new master cylinder. TEST the system for normal operation.
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N12 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. 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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