Pinpoint Test N: The Brake Warning Indicator is Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Test N: The Brake Warning Indicator is Always 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 B1048:7B. 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.
If the brake fluid level or parking brake status messages are missing for less than 5 seconds, the IPC (Instrument Panel Cluster) defaults the brake warning indicator to its last state (on or off) based upon the last known good message received. If the brake fluid level or parking brake status messages are missing for more than 5 seconds, the IPC (Instrument Panel Cluster) sets DTC U0140:00 and defaults the brake warning indicator on. If the IPC (Instrument Panel Cluster) does not receive the ABS status message or the EBD (Electronic Brake Distribution) message from the ABS module for more than 5 seconds, the IPC (Instrument Panel Cluster) sets DTC U0121:00 and defaults the ABS warning indicator on.
NOTE: If DTC U0140:00 sets in the IPC (Instrument Panel Cluster), other symptoms may also be present such as Tire Pressure Monitoring System (TPMS), instrument panel backlighting, and door ajar indication. If DTC U0121:00 is set, other symptoms may also be present such as ABS warning indicator and stability/traction control or stability/traction control off indicators always on.
NOTE: Both the ABS warning indicator and the brake warning indicator illuminate if the input to illuminate the brake warning indicator is received from the ABS module.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Parking brake warning indicator switch
- Brake fluid level switch
- ABS concern
- BCM (Body Control Module)
- IPC (Instrument Panel Cluster)
PINPOINT TEST N : 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.
N1 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 off. Observe the brake warning indicator.
Does the brake warning indicator turn off when commanded off?
Yes
GO to N2.
No
INSTALL a new IPC (Instrument Panel Cluster). REFER to Instrument Panel Cluster (IPC) . TEST the system for normal operation.
N2 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
For DTC U0121:00, GO to Pinpoint Test AV. Pinpoint Test AV: DTC U0121:00
For DTC U0140:00, GO to Pinpoint Test AY. Pinpoint Test AY: DTC U0140:00
For all other DTCs, REFER to DTC Charts. Instrumentation, Message Center and Warning Chimes
No
GO to N3.
N3 RETRIEVE THE RECORDED DTCs FROM THE BCM (Body Control Module) SELF-TEST
- Check for recorded BCM (Body Control Module) DTCs from the self-test.
Is DTC B1048:7B recorded?
Yes
GO to N8.
No
GO to N4.
N4 RETRIEVE THE RECORDED DTCs FROM THE ABS MODULE SELF-TEST
- Check for recorded ABS module DTCs from the self-test.
Are any DTCs recorded?
Yes
REFER to Antilock Brakes / Traction Control Systems.
No
GO to N5.
N5 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 and releasing the parking brake.
Does the PID agree with the parking brake position?
Yes
GO to N12.
No
GO to N6.
N6 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH
- Disconnect: Parking Brake Warning Indicator Switch C2015.
- 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.
Does the PID indicate the parking brake is released or off?
Yes
INSTALL a new parking brake warning indicator switch. CLEAR the DTCs. REPEAT the self-test.
No
GO to N7.
N7 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH INPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280C.
- Measure the resistance between the BCM (Body Control Module) C2280C-7, circuit CMC25 (WH/VT), harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to N12.
No
REPAIR circuit CMC25 (WH/VT) for a short to ground. CLEAR the DTCs. REPEAT the self-test.
N8 CHECK THE BRAKE WARNING INDICATOR USING THE 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.
Does the brake warning indicator turn off?
Yes
REMOVE the jumper wire. INSTALL a new brake fluid level switch. CLEAR the DTCs. REPEAT the self-test.
No
REMOVE the jumper wire. GO to N9.
N9 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT CIRCUIT FOR AN OPEN
- Ignition OFF.
- Disconnect: BCM (Body Control Module) C2280F.
- Measure the resistance between the BCM (Body Control Module) C2280F-15, 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 N10.
No
REPAIR circuit CMC19 (GY/VT) for an open. TEST the system for normal operation.
N10 CHECK THE BRAKE FLUID LEVEL SWITCH RETURN CIRCUIT FOR AN OPEN
- Measure the resistance between the BCM (Body Control Module) C2280F-1, 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 N11.
No
REPAIR circuit RMC19 (YE/GY) for an open. TEST the system for normal operation.
N11 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT AND RETURN CIRCUITS FOR A SHORT TO GROUND
- Measure the resistance between the BCM (Body Control Module) C2280F-15, circuit CMC19 (GY/VT), harness side and ground; and between the BCM (Body Control Module) C2280F-1, circuit RMC19 (YE/GY), harness side and ground.
Are the resistances greater than 10,000 ohms?
Yes
GO to N12.
No
REPAIR the circuit in question. TEST the system for normal operation.
N12 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.