Pinpoint Test M: The Brake Warning Indicator is Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Test M: The Brake Warning Indicator is Always On
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information Electrical Diagrams.
Normal Operation
The Instrument Panel Cluster (IPC) uses 3 basic 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 brake fluid level switch are hardwired to the IPC (Instrument Panel Cluster) through independent signal circuits. The EBD (Electronic Brake Distribution) message is sent from the ABS module over the High Speed Controller Area Network (HS-CAN) communication bus.
The IPC (Instrument Panel Cluster) 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 IPC (Instrument Panel Cluster) 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. The IPC (Instrument Panel Cluster) monitors the parking brake and the brake fluid level inputs and illuminates the brake warning indicator when the parking brake is applied or when the brake fluid level is low. When the ABS module detects a base brake system concern, other ABS-related or EBD (Electronic Brake Distribution) concerns, the ABS module sends a message to the IPC (Instrument Panel Cluster) to illuminate both the ABS warning indicator and the brake warning indicator.
If the EBD (Electronic Brake Distribution) message from the ABS module is missing for less than 5 seconds, the brake warning indicator remains in the last indication mode (on or off) based on the last known good message received. If the EBD (Electronic Brake Distribution) message from the ABS module is missing or deemed invalid for more than 5 seconds, the IPC (Instrument Panel Cluster) sets DTC U0121:00 and defaults the ABS warning indicator on. If the brake warning message received from the ABS module is deemed invalid by the IPC (Instrument Panel Cluster) for 5 seconds or more, the EBD (Electronic Brake Distribution) defaults the brake warning indicator on.
- DTC B1048:01 (Brake Fluid Level Switch: General Electrical Failure)- an on-demand DTC that sets in the IPC (Instrument Panel Cluster) if the IPC (Instrument Panel Cluster) detects a short to ground on the brake fluid level input circuit.
- DTC P1536:01 (Parking Brake Switch Circuit: General Electrical Failure)- an on-demand DTC that sets when the IPC (Instrument Panel Cluster) detects a short to ground on the parking brake warning indicator switch input circuit during the module self-test.
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.
NOTE: Both the ABS warning indicator and the brake warning indicator illuminate if the input to turn on 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
- IPC (Instrument Panel Cluster)
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.
M1 RETRIEVE THE RECORDED DIAGNOSTIC TROUBLE CODES (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 M2.
M2 CHECK THE OPERATION OF THE IPC (Instrument Panel Cluster)
- 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 active command (PBA_LMP). Command the brake warning indicator on then off while observing the brake warning indicator.
Does the brake warning indicator illuminate when commanded on and turn off when commanded off?
Yes
GO to M3.
No
INSTALL a new IPC (Instrument Panel Cluster). REFER to Instrument Panel Cluster (IPC) Service and Repair. TEST the system for normal operation.
M3 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH
- Ignition OFF.
- Disconnect: Parking Brake Warning Indicator Switch C306.
- Ignition ON.
- Monitor the brake warning indicator with the parking brake switch disconnected.
Does the brake warning indicator turn off?
Yes
INSTALL a new parking brake warning indicator switch. TEST the system for normal operation.
No
GO to M4.
M4 CHECK THE OPERATION OF THE BRAKE FLUID LEVEL SWITCH INPUT TO THE IPC (Instrument Panel Cluster)
NOTE: Verify that a low brake fluid level condition exists or existed prior to beginning the brake fluid level switch diagnostics.
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Ignition ON.
- Monitor the brake warning indicator.
Does the brake warning indicator turn off?
Yes
INSTALL a new brake fluid level switch. TEST the system for normal operation.
No
GO to M5.
M5 CHECK THE PARKING BRAKE SIGNAL CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: IPC (Instrument Panel Cluster) C220.
- Measure the resistance between the parking brake warning indicator switch C306-1, circuit CMC25 (WH/VT), harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to M6.
No
REPAIR circuit CMC25 (WH/VT) for a short to ground. TEST the system for normal operation.
M6 CHECK THE BRAKE FLUID LEVEL INPUT CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between the brake fluid level switch C124-2, circuit CE908 (BU/BN), harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to M7.
No
REPAIR circuit CE908 (BU/BN) for a short to ground. TEST the system for normal operation.
M7 CHECK FOR CORRECT IPC (Instrument Panel Cluster) OPERATION
- Disconnect all IPC (Instrument Panel Cluster) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all IPC (Instrument Panel Cluster) 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 IPC (Instrument Panel Cluster). REFER to Instrument Panel Cluster (IPC) Service and Repair. TEST the system for normal operation.
No
The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector.