Diagnostic Routine L
Diagnostic Routine L
Diagnostic Overview
The Brake Warning Indicator is Always On
Refer to Wiring Diagram Set 60 for schematic and connector information Electrical Diagrams.
Normal Operation and Fault Conditions
REFER to Brake Warning Indicator , REFER to Parking Brake Position Switch and REFER to Brake Fluid Level Switch .
NOTE: Both the ABS (Anti-Lock Brake System) warning indicator and the brake warning indicator illuminate if the input to illuminate the brake warning indicator is received from the ABS (Anti-Lock Brake System) module.
NOTE: If DTC (Diagnostic Trouble Code) U0140:00 sets in the IPC (Instrument Panel Cluster), other symptoms can also be present such as TPMS (Tire Pressure Monitoring System), instrument panel backlighting, and door ajar indication. If DTC (Diagnostic Trouble Code) U0121:00 sets, other symptoms can also be present such as ABS (Anti-Lock Brake System) warning indicator and traction control or traction control off indicators always on.
If the brake warning indicator request or brake (red) warning indicator request 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 warning indicator request message is missing for more than 5 seconds, the IPC (Instrument Panel Cluster) sets DTC (Diagnostic Trouble Code) U0140:00 and defaults the brake warning indicator on.
If the IPC (Instrument Panel Cluster) does not receive the brake (red) warning indicator request message from the ABS (Anti-Lock Brake System) module for more than 5 seconds, the IPC (Instrument Panel Cluster) sets DTC (Diagnostic Trouble Code) U0121:00 and defaults the ABS (Anti-Lock Brake System) warning indicator on.
BCM (Body Control Module) DTC Fault Trigger Conditions
Visual Inspection and Diagnostic Pre-checks
- Inspect the base brake system and the parking brake system for correct operation.
- Make sure the brake fluid level switch connector is connected and check for signs of connector terminal damage, corrosion or pushed out pins.
- Inspect the brake fluid level switch wiring for signs of a cut or opened circuit. Inspect the brake fluid level switch for signs of any external damage..
Pinpoint Test
1. CARRY OUT THE IPC (Instrument Panel Cluster) INDICATOR LAMP CONTROL ACTIVE COMMAND USING THE SCAN TOOL
1. Ignition ON.
2. Using a scan tool, view the IPC (Instrument Panel Cluster) PIDs (Parameter Identifications).
3. Select the IPC (Instrument Panel Cluster) brake warning indicator (PBA_LMP) PID (Parameter Identification). Command the brake warning indicator on and off. Observe the brake warning indicator.
Does the brake warning indicator turn off when commanded off?
2. RETRIEVE THE RECORDED DTCs (Diagnostic Trouble Codes) FROM THE IPC (Instrument Panel Cluster) SELF-TEST
1. Using a scan tool, perform the IPC (Instrument Panel Cluster) self-test.
Are any DTCs (Diagnostic Trouble Codes) recorded?
3. RETRIEVE THE RECORDED DTCs (Diagnostic Trouble Codes) FROM THE ABS (Anti-Lock Brake System) MODULE SELF-TEST
1. Using a scan tool, perform the ABS (Anti-Lock Brake System) module self-test.
Are any DTCs (Diagnostic Trouble Codes) recorded?
4. RETRIEVE THE RECORDED DTCs (Diagnostic Trouble Codes) FROM THE BCM (Body Control Module) SELF-TEST
1. Using a scan tool, perform the BCM (Body Control Module) self-test.
Is DTC (Diagnostic Trouble Code) B1048:01 recorded?
5. CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH PID (Parameter Identification) (PARK_BRK_SW)
1. Using a scan tool, view the BCM (Body Control Module) PIDs (Parameter Identifications).
2. Select the BCM (Body Control Module) parking brake (PARK_BRK_SW) PID (Parameter Identification).
3. Monitor the parking brake PID (Parameter Identification) while applying and releasing the parking brake.
Does the PID (Parameter Identification) agree with the parking brake position?
6. CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH
1. Disconnect: Parking Brake Position Switch.
2. Using a scan tool, view the BCM (Body Control Module) PIDs (Parameter Identifications).
3. Select the BCM (Body Control Module) parking brake (PARK_BRK_SW) PID (Parameter Identification).
4. Monitor the parking brake PID (Parameter Identification).
Does the PID (Parameter Identification) indicate the parking brake is released or off?
7. CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH INPUT CIRCUIT FOR A SHORT TO GROUND
1. Ignition OFF.
2. Disconnect: BCM (Body Control Module) C2280C.
3. Measure:
Is the resistance greater than 10,000 ohms?
8. CHECK THE BRAKE WARNING INDICATOR USING THE FLUID LEVEL SWITCH INPUT
1. Ignition OFF.
2. Disconnect: Brake Fluid Level Switch.
3. Connect a fused jumper wire:
4. Ignition ON.
Does the brake warning indicator turn off?
9. CHECK THE BRAKE FLUID LEVEL SWITCH INPUT CIRCUIT FOR AN OPEN
1. Ignition OFF.
2. Disconnect: BCM (Body Control Module) C2280F.
3. Measure:
Is the resistance less than 3 ohms?
10. CHECK THE BRAKE FLUID LEVEL SWITCH RETURN CIRCUIT FOR AN OPEN
1. Measure:
Is the resistance less than 3 ohms?
11. CHECK THE BRAKE FLUID LEVEL SWITCH INPUT AND RETURN CIRCUITS FOR A SHORT TO GROUND
1. Measure:
Are the resistances greater than 10,000 ohms?
12. CHECK FOR CORRECT BCM (Body Control Module) OPERATION
1. Ignition OFF.
2. Disconnect and inspect all BCM (Body Control Module) connectors.
3. Repair:
- corrosion (install new connector or terminals- clean module pins)
- damaged or bent pins- install new terminals/pins
- pushed-out pins- install new pins as necessary
4. Reconnect the BCM (Body Control Module) connectors. Make sure they seat and latch correctly.
5. Operate the system and determine if the concern is still present.
Is the concern still present?
