Pinpoint Test L: The Brake Warning Indicator Is Never On
Instrumentation, Message Center and Warning Chimes
Pinpoint Test L: The Brake Warning Indicator is Never On
Normal Operation
The Instrument Panel Cluster (IPC) uses 3 basic messaged inputs to control the brake warning indicator. The first two are the parking brake warning indicator switch and the brake fluid level switch. The third is for the Electronic Brake Distribution (EBD) function controlled by the ABS module. The parking brake warning indicator switch and the brake fluid level switch status are sent from the Body Control Module (BCM) over the High Speed Controller Area Network (HS-CAN). The EBD (Electronic Brake Distribution) message is sent from the ABS module over the HS-CAN (High Speed Controller Area Network).
The parking brake warning indicator switch is hardwired to the BCM (Body Control Module) through a single signal circuit while using a separate ground to control the input. The brake fluid level switch is hardwired to the BCM (Body Control Module) through separate signal and return circuits while using a separate ground to control the input.
The BCM (Body Control Module) 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, pulling the parking brake signal circuit low. When a low brake fluid level condition exists, the brake fluid level switch closes to ground, pulling the signal and return circuits low. If the brake fluid level switch is disconnected, the BCM (Body Control Module) reference voltage sent to the brake fluid level switch is sent high and the BCM (Body Control Module) sets DTC B1048:01. When the BCM (Body Control Module) detects either the brake fluid level signal or the parking brake signal circuits low, or the brake fluid level signal and return circuit high, the BCM (Body Control Module) sends the IPC (Instrument Panel Cluster) a brake warning indicator on request.
When the ABS module detects a base brake system concern or other ABS related concerns that affect the EBD (Electronic Brake Distribution) function, the ABS module sends a brake warning indicator on request to the IPC (Instrument Panel Cluster) to illuminate the brake warning indicator and the ABS warning indicator.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Brake fluid level switch
- Parking brake warning indicator switch
- BCM (Body Control Module)
- IPC (Instrument Panel Cluster)
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.
L1 RETRIEVE THE RECORDED DTCs FROM THE IPC (Instrument Panel Cluster) SELF-TEST
- Check for recorded IPC (Instrument Panel Cluster) DTCs from the self-test.
Are any DTCs recorded?
Yes
REFER to DTC Charts. Instrumentation, Message Center and Warning Chimes
No
GO to L2.
L2 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 L8.
No
GO to L3.
L3 CARRY OUT THE IPC (Instrument Panel Cluster) INDICATOR LAMP CONTROL ACTIVE COMMAND USING THE SCAN TOOL
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IPC (Instrument Panel Cluster) DataLogger.
- Select the IPC (Instrument Panel Cluster) brake warning indicator (PBA_LMP) 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 L4.
No
INSTALL a new IPC (Instrument Panel Cluster). REFER to Instrument Panel Cluster (IPC) Service and Repair. TEST the system for normal operation.
L4 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH PID
- Enter the following diagnostic mode on the scan tool: BCM (Body Control Module) DataLogger.
- Select the BCM (Body Control Module) parking brake (PARK_BRK_SW) PID. Monitor the parking brake PID while applying the parking brake.
Does the PID agree with the parking brake position?
Yes
GO to L12.
No
GO to L5.
L5 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH
- Disconnect: Parking Brake Warning Indicator Switch C2015.
- Connect a fused jumper wire between the parking brake warning indicator switch C2015-2, circuit GD133 (BK), harness side and the parking brake warning indicator switch C2015-1, 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 L6.
L6 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH GROUND CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between the parking brake warning indicator switch C2015-2, circuit GD133 (BK), harness side and ground.
Is the resistance less than 5 ohms?
Yes
GO to L7.
No
REPAIR circuit GD133 (BK) for an open. TEST the system for normal operation.
L7 CHECK THE PARKING BRAKE WARNING INDICATOR SIGNAL CIRCUIT FOR AN OPEN
- Disconnect: BCM (Body Control Module) C2280C.
- Measure the resistance between the BCM (Body Control Module) C2280C-7, circuit CMC25 (WH/VT), harness side and the parking brake warning indicator switch C2015-1, circuit CMC25 (WH/VT), harness side and ground.
Is the resistance less than 5 ohms?
Yes
GO to L12.
No
REPAIR circuit CMC25 (WH/VT) for an open. TEST the system for normal operation.
L8 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 L10.
No
GO to L9.
L9 CHECK THE BRAKE FLUID LEVEL SIGNAL AND RETURN CIRCUITS FOR A SHORT TOGETHER
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280F.
- Measure the resistance between the brake fluid level switch C124-2, circuit RMC19 (YE/GY), harness side and the brake fluid level switch C124-3, circuit CMC19 (GY/VT), harness side.
Is the resistance greater than 10,000 ohms?
Yes
GO to L12.
No
REPAIR the circuits. TEST the system for normal operation.
L10 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 GD120 (BK/GN), harness side and ground.
Is the resistance less than 5 ohms?
Yes
GO to L11.
No
REPAIR circuit GD120 (BK/GN) for an open. TEST the system for normal operation.
L11 CHECK THE BRAKE FLUID LEVEL SWITCH
- Connect: Brake Fluid Level Switch C124.
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: BCM (Body Control Module) DataLogger.
- 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.
- Monitor the BCM (Body Control Module) brake fluid PID (BRK_FLD_LVL).
Does the PID indicate LOW with the brake fluid level empty?
Yes
GO to L12.
No
INSTALL a new brake fluid level switch. TEST the system for normal operation.
L12 CHECK FOR CORRECT BCM (Body Control Module) OPERATION
- Disconnect all the BCM (Body Control Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the BCM (Body Control Module) 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 BCM (Body Control Module). 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.