Pinpoint Test M: The Brake Warning Indicator Is Always On
Instrumentation and Warning Chimes
Pinpoint Test
Pinpoint Test M: 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 messaged 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 module. The IC receives the parking brake warning indicator switch input through a single hardwired circuit and the brake fluid level switch input through separate hardwired input and return circuits. The EBD message is sent from the ABS module over the High Speed Controller Area Network (HS-CAN) communication bus lines.
The IC 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, providing a ground to the IC and pulling the signal circuit low. When a low brake fluid level condition exists, the low brake fluid level switch closes to ground, pulling the signal circuit low. 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.
- DTC C1125 (Brake Fluid Level Sensor Input Circuit Failure) - a continuous and on-demand DTC that sets when the IC detects an open in the brake fluid level switch input or return circuits or a disconnected brake fluid level switch.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Parking brake switch
- Brake fluid level switch
- ABS module
- IC
PINPOINT TEST M: 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 continuing with diagnostics.
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M1 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 then off again. Observe the brake warning indicator.
- Does the brake warning indicator turn off when commanded off?
Yes
GO to M2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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M2 RETRIEVE THE RECORDED DTCs FROM THE ABS MODULE SELF-TEST
- Use the recorded ABS module DTCs from the self-test.
- Are any DTCs retrieved?
Yes
REFER to Antilock Brakes / Traction Control Systems.
No
GO to M3.
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M3 RETRIEVE THE RECORDED DTCs FROM THE IC SELF-TEST
- Check for recorded DTCs from the IC self-test.
- Are any DTCs recorded?
Yes
For DTC C1125, GO to M6.
For DTC U0121:00, GO to Pinpoint Test AM. Pinpoint Tests AM: DTC U0121
For all other DTCs, REFER to DTC Charts. [1][2]Diagnostic Trouble Code Descriptions
No
GO to M4.
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M4 CHECK THE PARKING BRAKE SWITCH
- Ignition OFF.
- Disconnect: Parking Brake Switch C2015.
- Ignition ON.
- Observe the brake warning indicator.
- Did the brake warning indicator turn off?
Yes
INSTALL a new parking brake switch. TEST the system for normal operation.
No
GO to M5.
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M5 CHECK THE PARKING BRAKE INPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: IC C220b.
- Measure the resistance between the parking brake switch C2015-1, circuit CCB09 (GY/BU), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to M10.
No
REPAIR circuit CCB09 (GY/BU) for a short to ground. TEST the system for normal operation.
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M6 CHECK THE BRAKE FLUID LEVEL SWITCH
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Connect a fused jumper wire 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.
- Ignition ON.
- Monitor the brake warning indicator.
- Does the brake warning indicator turn off?
Yes
REMOVE the jumper wire. INSTALL a new brake fluid level switch. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to M7.
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M7 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: IC C220b.
- Measure the resistance between the IC C220b-18, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-2, circuit CMC19 (GY/VT), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to M8.
No
REPAIR circuit CMC19 (GY/VT) for an open. TEST the system for normal operation.
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M8 CHECK THE BRAKE FLUID LEVEL SWITCH RETURN CIRCUIT FOR AN OPEN
- Measure the resistance between the IC C220b-19, circuit RMC19 (YE/GY), harness side and the brake fluid level switch C124-3, circuit RMC19 (YE/GY), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to M9.
No
REPAIR circuit RMC19 (YE/GY) for an open. TEST the system for normal operation.
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M9 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT AND RETURN CIRCUITS FOR A SHORT TO GROUND
- Measure the resistance between the IC C220b-18, circuit CMC19 (GY/VT), harness side and ground; and between the IC C220b-19, circuit RMC19 (YE/GY), harness side and ground.
- Are the resistances greater than 10,000 ohms?
Yes
GO to M10.
No
REPAIR the circuit in question. TEST the system for normal operation.
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M10 CHECK FOR CORRECT IC OPERATION
- Disconnect all the IC connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all 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) Instrument Cluster (IC). 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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