Pinpoint Test L: The Brake Warning Indicator Is Never On
Instrumentation and Warning Chimes
Pinpoint Test
Pinpoint Test L: 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 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.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Parking brake switch
- Brake fluid level switch
- IC
PINPOINT TEST L: 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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L1 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 L2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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L2 CHECK THE PARKING BRAKE INPUT TO THE IC
- Enter the following diagnostic mode on the scan tool: IC DataLogger.
- Monitor the IC parking brake input PID (PRKSWAPPL) while applying the parking brake.
- Does the parking brake PID indicate ON when the parking brake is applied?
Yes
GO to L6.
No
GO to L3.
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L3 CHECK THE PARKING BRAKE SWITCH
- Ignition OFF.
- Disconnect: Parking Brake Switch C2015.
- Connect a fused jumper wire between the parking brake switch C2015-1, circuit CCB09 (GY/BU), harness side and the parking brake switch C2015-2, circuit GD175 (BK/BU), harness side.
- Ignition ON.
- Does the brake warning indicator illuminate?
Yes
INSTALL a new parking brake switch. TEST the system for normal operation.
No
REMOVE the jumper wire. GO to L4.
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L4 CHECK THE PARKING BRAKE SWITCH GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between the parking brake switch C2015-2, circuit GD175 (BK/BU), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to I5. Pinpoint Test I: Incorrect Tachometer Indication
No
REPAIR circuit GD175 (BK/BU) for an open. TEST the system for normal operation.
L5 CHECK THE PARKING BRAKE SWITCH INPUT CIRCUIT FOR AN OPEN
- Disconnect: IC C220b.
- Measure the resistance between the IC C220b-20, circuit CCB09 (GY/BU), harness side and the parking brake switch C2015-1, circuit CCB09 (GY/BU), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to L9.
No
REPAIR circuit CCB09 (GY/BU) for an open. TEST the system for normal operation.
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L6 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT
NOTE: Verify that the brake fluid level is low or was low prior to a brake system repair before continuing with diagnostics.
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Ignition ON.
- Does the brake warning indicator illuminate?
Yes
GO to L8.
No
GO to L7.
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L7 CHECK THE BRAKE FLUID LEVEL INPUT AND RETURN CIRCUITS FOR A SHORT TOGETHER
- Ignition OFF.
- Disconnect: IC C220b.
- 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 L9.
No
REPAIR the circuit in question for a short together. TEST the system for normal operation.
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L8 CHECK THE BRAKE FLUID LEVEL SWITCH GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between the brake fluid level switch C124-1, circuit GD175 (BK/BU), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new brake fluid level switch. TEST the system for normal operation.
No
REPAIR circuit GD175 (BK/BU) for an open. TEST the system for normal operation.
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L9 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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