Pinpoint Test N: The Brake Warning Indicator Is Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test N: The Brake Warning Indicator Is Always On
Refer to Wiring Diagram Set 60, Instrument Cluster for schematic and connector information. Diagrams By Number
Normal Operation
The brake warning indicator alerts the driver if any of the following brake system conditions are present: the parking brake is set, the brake fluid level is low or the ABS module detects an Electronic Brake Distribution (EBD) failure.
When the parking brake is applied, the parking brake warning indicator switch grounds the parking brake input circuit to the Smart Junction Box (SJB). The SJB detects the ground signal and sends the IC a message over the Medium Speed Controller Area Network (MS-CAN) to illuminate the brake warning indicator.
The MS-CAN provides a reference voltage to the brake fluid level switch on the input circuit. When the brake fluid level is low, the brake fluid level switch closes the input circuit to ground, pulling the reference low. When the SJB detects the reference voltage pulled low, the SJB sends a message to the IC over the MS-CAN to turn on the brake warning indicator.
When an EBD failure is detected, the ABS module sends a signal to the IC over the communication network to illuminate the brake system warning indicator.
If the parking brake or brake fluid level status message is missing for less than 5 seconds, the brake warning remains in the last indication mode (on or off). If the parking brake or brake fluid level status message is missing for more than 5 seconds, the IC sets DTC U0140 in continuous memory and defaults the brake warning indicator on. If the IC loses communication with the ABS module or the ABS module is disconnected, the IC sets DTC U0121 in continuous memory and defaults the brake warning indicator on.
- DTC B2479 (Brake Park Switch Circuit Short to Ground) - an on-demand DTC that sets if the SJB detects a short to ground on the parking brake input circuit, during a self-test.
- DTC C1125 (Brake Fluid Level Sensor Input Circuit Failure) - a continuous and on-demand DTC that sets if the SJB detects an open or short to ground on the brake fluid level switch input circuit. If the brake fluid level switch is disconnected, the IC sets DTC C1125 and defaults the brake warning indicator on.
NOTE: If DTC U0121 is set in the IC, the ABS warning indicator is also illuminated.
NOTE: If DTC U0140 is set in the IC, other observable symptoms may also be present such as Tire Pressure Monitoring System (TPMS) warning indicator, backlighting and door ajar indication.
NOTE: If the brake system experiences an EBD failure, both the brake warning indicator and the ABS warning indicator illuminate.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Parking brake warning indicator switch
- Brake fluid level switch
- SJB
- IC
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.
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N1 CHECK THE ABS WARNING LIGHT OPERATION
- Ignition ON.
- Observe the ABS warning indicator and brake warning indicators following the IC prove-out.
- Are both the ABS and brake warning indicators illuminated?
Yes
GO to Pinpoint Test O. Pinpoint Test O: The ABS Warning Indicator Is Never/Always On
No
GO to N2.
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N2 CARRY OUT THE IC INDICATOR LAMP CONTROL ACTIVE COMMAND USING THE SCAN TOOL
- Enter the following diagnostic mode on the scan tool: IC DataLogger.
- Select the IC brake warning indicator (BRK_LAMP) active command and command the brake warning indicator on and off. Observe the brake warning indicator.
- Does the brake warning indicator illuminate when commanded on and turn off when commanded off?
Yes
GO to N3.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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N3 RETRIEVE THE RECORDED DTCs FROM THE IC SELF-TEST
- Check for recorded IC DTCs from the self-test.
- Are any DTCs recorded?
Yes
For DTC U0121, GO to Pinpoint Test AW. Pinpoint Tests AW: DTC U0121
For DTC U0140, GO to Pinpoint Test AX. Pinpoint Tests AX: DTC U0140
For all other DTCs, REFER to DTC Charts. Instrumentation, Message Center and Warning Chimes
No
GO to N4.
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N4 RETRIEVE THE RECORDED DTCs FROM THE ABS MODULE SELF-TEST
- Check for recorded ABS module DTCs from the self-test.
- Are any ABS module DTCs recorded?
Yes
REFER to Antilock Brakes / Traction Control Systems.
No
GO to N5.
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N5 RETRIEVE THE RECORDED DTCs FROM THE SJB SELF-TEST
- Check for recorded SJB DTCs from the self-test.
- Are any SJB DTCs recorded?
Yes
For DTC B2479, GO to N6.
For DTC C1125, GO to N8.
All other SJB DTCs, REFER to DTC Charts. Instrumentation, Message Center and Warning Chimes
No
GO to N12.
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N6 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH
- Disconnect: Parking Brake Warning Indicator Switch C2015.
- Observe the brake warning indicator.
- Does the brake warning indicator continue to illuminate?
Yes
GO to N7.
No
INSTALL a new parking brake warning indicator switch. REFER to Parking Brake System. CLEAR the DTCs. REPEAT the self-test.
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N7 CHECK THE SJB PARKING BRAKE WARNING INDICATOR SWITCH INPUT CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: SJB C2280c.
- Measure the resistance between the SJB C2280c-1, circuit CLS05 (BU/GY), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to N11.
No
REPAIR circuit CLS05 (BU/GY) for a short to ground. CLEAR the DTCs. REPEAT the self-test.
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N8 CHECK THE SJB OPERATION USING THE SCAN TOOL
- 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.
- Monitor the brake warning indicator.
- Does the brake warning indicator turn off?
Yes
REMOVE the jumper wire. INSTALL a new brake master cylinder. REFER to Hydraulic System, Brakes &/or Brake Pedal Assy. CLEAR the DTCs. REPEAT the self-test.
No
REMOVE the jumper wire. GO to N9.
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N9 CHECK THE BRAKE FLUID LEVEL SWITCH INPUT CIRCUIT FOR AN OPEN AND SHORT TO GROUND
- Ignition OFF.
- Disconnect: SJB C2280f.
- Measure the resistance between the SJB C2280f-9, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-2, circuit CMC19 (GY/VT), harness side; and between the SJB C2280f-9, circuit CMC19 (GY/VT), harness side and ground.
- Is the resistance less than 5 ohms between the SJB and the brake fluid level switch, and greater than 10,000 ohms between the SJB and ground?
Yes
GO to N10.
No
REPAIR circuit CMC19 (GY/VT) for an open or short to ground. CLEAR the DTCs. REPEAT the self-test.
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N10 CHECK THE BRAKE FLUID LEVEL SWITCH RETURN CIRCUIT FOR AN OPEN AND SHORT TO GROUND
- Measure the resistance between the SJB C2280f-22, circuit RMC19 (YE/GY), harness side and the brake fluid level switch C124-3, circuit RMC19 (YE/GY), harness side; and between the SJB C2280f-22, circuit RMC19 (YE/GY), harness side and ground.
- Is the resistance less than 5 ohms between the SJB and the brake fluid level switch, and greater than 10,000 ohms between the SJB and ground?
Yes
GO to N11.
No
REPAIR circuit RMC19 (YE/GY) for an open or short to ground. CLEAR the DTCs. REPEAT the self-test.
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N11 CHECK FOR CORRECT SJB OPERATION
- Disconnect all the SJB connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the SJB connectors and make sure they seat correctly.
- Operate the system and verify that the concern is still present.
- Is the concern still present?
Yes
INSTALL a new SJB. REFER to Body Control Systems. 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. CLEAR the DTCs. REPEAT the self-test.
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N12 CHECK FOR CORRECT IC OPERATION
- Disconnect the IC connector.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the IC connector and make sure it seats correctly.
- Operate the system and verify that 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. CLEAR the DTCs. REPEAT the self-test.
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