Pinpoint Test K: The Brake Warning Indicator Is Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test K: The Brake Warning Indicator Is Always On
Refer to Wiring Diagram Set 60 (Escape/Mariner, Escape Hybrid/Mariner Hybrid), Instrument Cluster for schematic and connector information. Diagrams By Number
Normal Operation
The IC uses 3 basic messaged 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 module. The parking brake warning indicator switch status is sent from the Smart Junction Box (SJB) over the Medium Speed Controller Area Network (MS-CAN) communication bus. The brake fluid level switch status is sent from the SJB over the MS-CAN. The EBD message is sent from the ABS module over the High Speed Controller Area Network (HS-CAN) communication bus lines. The parking brake warning indicator switch is hardwired to the SJB through signal circuit CMC25 (WH/VT). The brake fluid level switch is hardwired to the SJB through signal circuit CMC19 (GY/VT).
The SJB provides a reference voltage to both the parking brake switch and the brake fluid level switch. When the parking brake is applied, the parking brake warning indicator switch closes to ground through circuit GD182 (BK/GY), providing a ground to the SJB and pulling signal circuit CMC25 (WH/VT) low. When a low brake fluid level condition exists, the low brake fluid level switch closes to ground through circuit GD120 (BK/GN), pulling signal circuit CMC19 (GY/VT) low. The SJB monitors the parking brake input and sends the IC a message to turn the brake warning indicator on when the parking brake is applied. The SJB monitors the brake fluid level and sends the IC a message to turn on the brake warning indicator when a low brake fluid level condition exists. When the ABS module detects a base brake system concern or other ABS related concerns that affect the EBD function, the ABS module sends a message to the IC to illuminate both the ABS warning indicator and the brake warning indicator.
If the brake fluid level or parking brake status messages are missing or deemed invalid by the IC for more than 5 seconds, the IC sets DTC U0140 and defaults the brake warning indicator on. If the IC does not receive the ABS status message or the EBD message from the ABS module or the message is deemed invalid by the IC for greater than 5 seconds, the IC sets DTC U0121 (except Hybrid) or U0129 (Hybrid only) and defaults the ABS warning indicator on.
- DTC B2479 (Park Brake Switch Circuit Short to Ground) - an on-demand DTC that sets when the SJB detects a short to ground on the parking brake warning indicator switch input, circuit CMC25 (WH/VT) during the module self-test.
- DTC C1125 (Brake Fluid Level Sensor Input Circuit Failure) - a continuous and on-demand DTC that sets in the SJB if the SJB detects a short to ground on the brake fluid level input circuit CMC19 (GY/VT).
NOTE: If DTC U0140 is set in the IC, 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 module
- SJB
- IC
PINPOINT TEST K: 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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K1 CARRY OUT THE IC INDICATOR LAMP CONTROL ACTIVE COMMAND USING THE SCAN TOOL
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IC DataLogger.
- Select the IC brake warning indicator (BRK_LAMP) 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 K2.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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K2 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 U0140, Go To Pinpoint Test AZ. Pinpoint Tests AZ: DTC U0140
For DTC U0121 (except Hybrid), Go To Pinpoint Test AW. Pinpoint Tests AW: DTC U0121
For DTC U0129 (Hybrid only), Go To Pinpoint Test AX. Pinpoint Tests AX: DTC U0129
For all other DTCs, REFER to DTC Charts. Instrumentation, Message Center and Warning Chimes
No
GO to K3.
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K3 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. Testing and Inspection
No
GO to K4.
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K4 RETRIEVE THE RECORDED DTCs FROM THE SJB SELF-TEST
- Check for recorded SJB DTCs from the self-test.
- Is DTC B2479 recorded?
Yes
GO to K5.
No
GO to K8.
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K5 CHECK THE PARKING BRAKE SWITCH PID
- Enter the following diagnostic mode on the scan tool: SJB DataLogger.
- Select the SJB parking brake (PRK_BRAKE) 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 K10.
No
GO to K6.
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K6 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 K7.
No
INSTALL a new parking brake warning indicator switch. CLEAR the DTCs. REPEAT the self-test.
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K7 CHECK CIRCUIT CMC25 (WH/VT) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: SJB C2280c.
- Measure the resistance between the SJB C2280c-1, circuit CMC25 (WH/VT), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to K10.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
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K8 CHECK THE BRAKE FLUID LEVEL SWITCH OPERATION
- Ignition OFF.
- Disconnect: Brake Fluid Level Switch C124.
- Ignition ON.
- Does the brake warning indicator turn off?
Yes
INSTALL a new brake fluid level switch. CLEAR the DTCs. REPEAT the self-test.
No
GO to K9.
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K9 CHECK CIRCUIT CMC19 (GY/VT) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: SJB C2280F.
- Measure the resistance between the SJB C2280f-9, circuit CMC19 (GY/VT), harness side and ground.
- Is the resistance less than 10,000 ohms?
Yes
GO to K10.
No
REPAIR the circuit. REPEAT the self-test.
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K10 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. 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.
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