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Pinpoint Test L: The Brake Warning Indicator Is Never On

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Instrument Cluster for schematic and connector information.

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 a electronic brake distribution (EBD) failure. If the brake system experiences an EBD failure, both the brake warning indicator and the ABS warning indicator illuminate.

When the parking brake is applied, the parking brake warning indicator switch grounds circuit CLS05 (BU/GY) to the smart junction box (SJB). The SJB detects the ground signal and sends the instrument cluster (IC) a message over the medium speed controller area network (MS-CAN) to illuminate the brake warning indicator.

The SJB provides a reference voltage to the brake fluid level switch on input circuit CMC19 (GY/VT) with the signal return on circuit RMC19 (YE/GY). The brake fluid level switch is grounded through circuit GD120 (BK/GN). When the brake fluid level is low, the brake fluid level switch closes the input signal circuit to ground, pulling the reference low. When the SJB detects the reference voltage pulled low, the SJB sends a message to the instrument cluster (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 instrument cluster (IC) over the communication network to illuminate the brake system warning indicator.

This pinpoint test is intended to diagnose the following:

PINPOINT TEST L: THE BRAKE WARNING INDICATOR IS NEVER ON 

NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. L1 CARRY OUT THE INSTRUMENT CLUSTER (IC) INDICATOR LAMP ACTIVE COMMAND USING THE SCAN TOOL 
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: Instrument Cluster (IC) DataLogger
    • Select the instrument cluster (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? 
    1. YES  : Go to  L2.
    2. NO  : Go to  L9.
  2. L2 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH PID 
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: SJB DataLogger
    • Monitor the SJB parking brake warning indicator switch (PRK_BRAKE) PID while applying the parking brake.
    • Does the PID indicate ACTIVE with the parking brake applied? 
    1. YES  : Go to  L5.
    2. NO  : Go to  L3.
  3. L3 CHECK THE PARKING BRAKE WARNING INDICATOR SWITCH 
    • Disconnect: Parking Brake Warning Indicator Switch C2015
      • Fig 1: Checking Parking Brake Warning Indicator Switch
      GF0030388Courtesy of FORD MOTOR CO.
    • Connect a fused (5A) jumper wire between the parking brake warning indicator switch C2015-1, circuit CLS05 (BU/GY), harness side and ground.
    • Does the brake warning indicator illuminate? 
    1. YES  : REMOVE the jumper wire. INSTALL a new parking brake warning indicator switch. REFER to PARKING BRAKE & ACTUATION article. TEST the system for normal operation.
    2. NO  : REMOVE the jumper wire. Go to  L4.
  4. L4 CHECK CIRCUIT CLS05 (BU/GY) FOR AN OPEN 
    • Disconnect: SJB C2280c
      • Fig 2: Measuring Resistance Between SJB C2280C-1, Circuit CLS05 (BU/GY) & Parking Brake Switch C2015-1
      GF0032211Courtesy of FORD MOTOR CO.
    • Measure the resistance between the SJB C2280c-1, circuit CLS05 (BU/GY), harness side and the parking brake warning indicator switch C2015-1, circuit CLS05 (BU/GY), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  L8.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  5. L5 CHECK THE SJB OPERATION USING THE SCAN TOOL 
    • Key in OFF position.
    • Disconnect: Brake Fluid Level Switch C124
      • Fig 3: Connecting Fused (5A) Jumper Wire Between Brake Fluid Level Switch C124-2 & C124-1, CMC19 (GY/VT) & GD120 (BK/GN)
      GF0032212Courtesy of FORD MOTOR CO.
    • Connect a fused (5A) jumper wire between the brake fluid level switch C124-2, circuit CMC19 (GY/VT), harness side and the brake fluid level switch C124-1, circuit GD120 (BK/GN), harness side.
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: SJB DataLogger
    • Monitor the brake fluid level (BRK_FLD_ST) PID.
    • Does the PID indicate LOW with the jumper wire in place? 
    1. YES  : REMOVE the jumper wire. Go to  L7.
    2. NO  : REMOVE the jumper wire. Go to  L6.
  6. L6 CHECK CIRCUIT GD120 (BK/GN) FOR AN OPEN 
    • Key in OFF position.
      • Fig 4: Checking Circuit For Open
      GF0014462Courtesy of FORD MOTOR CO.
    • 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? 
    1. YES  : Go to  L7.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  7. L7 CHECK THE BRAKE FLUID LEVEL SWITCH PID USING THE SCAN TOOL 
    • Connect: Brake Fluid Level Switch C124
    • Key in ON position.
    • Enter the following diagnostic mode on the diagnostic tool: SJB DataLogger
      • NOTE: Verify that the brake fluid reservoir is empty.
    • Monitor the SJB brake fluid (BRK_FLD_ST) PID.
    • Does the PID indicate LOW with the brake fluid level empty? 
    1. YES  : Go to  L8.
    2. NO  : INSTALL a new brake master cylinder. REFER to HYDRAULIC BRAKE ACTUATION article. TEST the system for normal operation.
  8. L8 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? 
    1. YES  : INSTALL a new SJB. REFER to MULTIFUNCTION ELECTRONIC MODULES article. TEST the system for normal operation.
    2. 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.
  9. L9 CHECK FOR CORRECT INSTRUMENT CLUSTER (IC) OPERATION 
    • Disconnect the instrument cluster (IC) connector.
    • Check for:
      • corrosion
      • damaged pins
      • pushed-out pins
    • Connect the instrument cluster (IC) connector and make sure it seats correctly.
    • Operate the system and verify that the concern is still present.
    • Is the concern still present? 
    1. YES  : INSTALL a new instrument cluster (IC). REFER to Instrument Cluster (IC) . TEST the system for normal operation.
    2. 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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