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Normal Operation and Fault Conditions

WARNING: This page is about a different car, the 2020 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.

The trail control switch is used to activate and deactivate the trail control feature. When the driver presses the trail control switch, the IPC receives a ground signal from the switch and illuminates the trail control indicator. The IPC sends a trail control switch message to the GWM over the HS-CAN 3 and the GWM relays this message to the ABS module over the HS-CAN 2. The ABS module adjusts the operating parameters of the anti-lock and stability control features, and aids in maintaining the set speed of the vehicle. Vehicle speed is adjusted using the cruise control steering wheel switches. 

The driver door ajar switch is hard-wired to the ABS module for trail control feature safety operation. When the trail control feature is enabled and active, and the driver door is opened, the IPC notifies the occupants through the message center and the driving torque propelling the vehicle is disabled. If descending an incline, the ABS maintains the descent speed until the vehicle is no longer on an incline. If ascending an incline, the vehicle rolls backward at a speed of 3 km/h (2 mph) until it is no longer on an incline. 

PPT CI ABS MODULE DTC FAULT TRIGGER CONDITIONS

DTC Description Fault Trigger Conditions
P166B:11 Drivers Door Status Correlation: Short to Ground This DTC sets when the hard-wired driver door ajar switch circuit is shorted to ground.
P166B:12 Drivers Door Status Correlation: Short to Battery This DTC sets when the hard-wired driver door ajar switch circuit is shorted to voltage.
P166B:64 Drivers Door Status Correlation: Signal Plausibility Failure The ABS module also receives a driver door ajar message from the BCM and compares the hard-wired door ajar input to the message. If the hard-wired switch state does not match the message and DTC P166B:11 or P166B:12 is not set, then this DTC sets.
NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.
Fig 1: Antilock Braking System (ABS) Module Connector - C135
G13431532Courtesy of FORD MOTOR CO.

Harness Side

Circuit Pin
Fig 2: Instrument Panel Control Module (IPC) Connector - C220
G13431533Courtesy of FORD MOTOR CO.

Harness Side

Circuit Pin
  1. CI1: VERIFY CRUISE CONTROL OPERATION 
    • Test drive the vehicle to verify the cruise control system functions correctly.
    • Does the cruise control system operate correctly? 
      Yes No
      Go to  CI2. REFER to the Cruise Control article to diagnose the cruise control system.
  2. CI2: VERIFY PARKING BRAKE OPERATION 
    • Operate the parking brake system and verify it operates correctly.
    • Does the parking brake system operate correctly? 
      Yes No
      Go to  CI3. DIAGNOSE the parking brake system. REFER to the Parking Brake and Actuation article.
  3. CI3: CHECK THE ABS MODULE FOR DTCS 
    • Ignition ON, engine OFF.

      Carry out the ABS self-test.

    • Are any of the DTCs listed in the Fault Trigger Conditions Table present in the ABS module? 
      Yes No
      RETRIEVE and RECORD all ABS module DTCs.
      Go to  CI9.      		 For all other ABS module DTCs, GO to the ABS Module DTC Chart.
      If there are no DTCs present in the ABS module, Go to  CI4.
  4. CI4: CHECK FOR DTCS IN TRAIL CONTROL RELATED MODULES 
    • Ignition ON, engine OFF.

      Carry out the IPC self-test.

      Carry out the PCM KOEO self-test.

      Carry out the SCCM self-test.

    • Are there any DTCs present in any of the listed modules? 
      Yes No
      For IPC DTCs, REFER to the Cruise Control article.
      For PCM DTCs, REFER to the appropriate Electronic Engine Controls article.
      For SCCM DTCs, REFER to the Steering Wheel and Column Electrical Components article.      		 Go to  CI5.
  5. CI5: CHECK THE SWITCH FOR AN OPEN OR A SHORT 
    • Ignition OFF.
    • Press and hold the switch while taking the measurement.
    • Measure the resistance between:
      (+) CSS Connector, Component Side (-) CSS Connector, Component Side
      TC GND
    • Measure the resistance between:
      (+) Hazard Switch Connector, Component Side (-) Hazard Switch Connector, Component Side
      HDC GND
    • Release the switch and take another measurement.
    • Measure the resistance between:
      (+) CSS Connector, Component Side (-) CSS Connector, Component Side
      TC GND
    • Measure the resistance between:
      (+) Hazard Switch Connector, Component Side (-) Hazard Switch Connector, Component Side
      HDC GND
    • Is the resistance less than 3 ohms with the switch pressed and greater than 10, 000 ohms with the switch released? 
      Yes No
      Go to  CI6. INSTALL a new Hazard switch.
      INSTALL a new hazard switch (the trail control switch is part of the hazard switch).
  6. CI6: CHECK THE TRAIL CONTROL SWITCH GROUND CIRCUIT FOR AN OPEN 
    • Measure the resistance between:
      (+) CSS Connector, Harness Side (-)
      GND Ground
    • Measure the resistance between:
      (+) Hazard Switch Connector, Harness Side (-)
      GND Ground
    • Is the resistance less than 3 ohms? 
      Yes No
      Go to  CI7. REPAIR the circuit.
  7. CI7: CHECK THE TRAIL CONTROL SWITCH SIGNAL CIRCUIT FOR AN OPEN 
    • IPC connector disconnected. (C220)
    • Measure the resistance between:
      (+) CSS Connector, Harness Side (-) IPC (C220) Connector, Harness Side
      TC TC
    • Measure the resistance between:
      (+) Hazard Switch Connector, Harness Side (-) IPC (C220) Connector, Harness Side
      HDC HDC
    • Is the resistance less than 3 ohms? 
      Yes No
      Go to  CI8. REPAIR the circuit.
  8. CI8: CHECK THE TRAIL CONTROL SWITCH SIGNAL CIRCUIT FOR A SHORT TO GROUND 
    • Measure the resistance between:
      (+) CSS Connector, Harness Side (-)
      TC Ground
    • Measure the resistance between:
      (+) Hazard Switch Connector, Harness Side (-)
      HDC Ground
    • Is the resistance greater than 10, 000 ohms? 
      Yes No
      Go to  CI17. REPAIR the circuit.
  9. CI9: CHECK THE BCM FOR DTCS 
    • Ignition ON, engine OFF.

      Carry out the BdyCM self-test.

    • Are any door ajar switch DTCs present in the BCM? 
      Yes No
      RETRIEVE and RECORD all BCM DTCs. REFER to the Multifunction Electronic Modules article. Go to  CI10.
  10. CI10: CHECK THE DRIVER DOOR SWITCH FOR AN OPEN OR A SHORT 
    • Ignition OFF.
    • Take the following measurement with the driver door switch in the OPEN position.
    • Measure the resistance between:
      (+) Driver Door Ajar Switch Connector, Component Side (-) Driver Door Ajar Switch Connector, Component Side
      D_DOOR GND
    • Note the resistance reading.
    • Close the driver door switch.
    • Measure the resistance between:
      (+) Driver Door Ajar Switch Connector, Component Side (-) Driver Door Ajar Switch Connector, Component Side
      D_DOOR GND
    • Is the resistance greater than 10, 000 ohms with the switch open and less than 3 ohms with the switch closed? 
      Yes No
      Go to  CI11. Install a new driver door latch assembly, the door ajar switch is part of the latch assembly. REFER to the Handles, Locks, Latches and Entry Systems article.
  11. CI11: CHECK THE DRIVER DOOR AJAR SWTICH GROUND CIRCUIT FOR AN OPEN 
    • Measure the resistance between:
      (+) Driver Door Ajar Switch Connector, Harness Side (-)
      GND Ground
    • Is the resistance less than 3 ohms? 
      Yes No
      Go to  CI12. REPAIR the circuit.
  12. CI12: CHECK THE DRIVER DOOR AJAR SWTICH CIRCUIT FOR AN OPEN 
    • ABS Module connector disconnected. (C135)
    • Measure the resistance between:
      (+) Driver Door Ajar Switch Connector, Harness Side (-) ABS Module (C135) Connector, Harness Side
      D_DOOR D_DOOR
    • Is the resistance less than 3 ohms? 
      Yes No
      Go to  CI13. REPAIR the circuit.
  13. CI13: CHECK THE DRIVER DOOR AJAR SWTICH CIRCUIT FOR A SHORT TO GROUND 
    • Measure the resistance between:
      (+) Driver Door Ajar Switch Connector, Harness Side (-)
      D_DOOR Ground
    • Is the resistance greater than 10, 000 ohms? 
      Yes No
      Go to  CI14. REPAIR the circuit.
  14. CI14: CHECK THE DRIVER DOOR AJAR SWTICH CIRCUIT FOR A SHORT TO VOLTAGE 
    NOTE: This test step causes ABS related DTCs to set in other modules. These DTCs must be cleared once these diagnostics are complete.
    • Ignition ON, engine OFF.
    • Measure the voltage between:
      (+) Driver Door Ajar Switch Connector, Harness Side (-)
      D_DOOR Ground
    • Is any voltage present? 
      Yes No
      REPAIR the circuit. Go to  CI15.
  15. CI15: VERIFY ALL WIRING CONNECTIONS 
    • Using a good light source, inspect all disconnected electrical connectors for the following:
      • corrosion - install new connector or terminal and clean the module pins
      • damaged or bent pins - install new terminals or pins
      • pushed-out pins - install new pins as necessary
      • spread terminals - install new terminals as necessary
    • Are the connectors free of corrosion, damaged pins, bent pins, pushed-out pins and spread terminals? 
      Yes No
      Go to  CI16. REPAIR the affected connectors or terminals. REFER to the Connector Repair Procedures wiring diagrams for schematic and connector information.
  16. CI16: CHECK FOR CORRECT ABS MODULE OPERATION 
    • Ignition OFF.
    • Driver Door Ajar Switch connector connected. Make sure the connector seats and latches correctly.
    • ABS Module connector connected. (C135) Make sure the connector seats and latches correctly.
    • Operate the system and determine if the concern is still present.
    • Is the concern still present? 
      Yes No
      INSTALL a new ABS module.
      CHECK OASIS for any service articles: TSB, GSB, SSM or FSA.
      If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions.
      If no services articles address this concern, INSTALL a new ABS module. REFER to the Anti-Lock Brake System (ABS) and Stability Control article.
      ORDER a replacement ABS module and INCLUDE the RVC on the form.
      If this is a Ford paid repair, INCLUDE the RVC on the warranty claim form.
      Using a diagnostic scan tool, CARRY OUT a network test. CLEAR all ABS related DTCs from any reporting modules.      		 The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.
      Using a diagnostic scan tool, CARRY OUT a network test. CLEAR all ABS related DTCs from any reporting modules.
  17. CI17: VERIFY ALL WIRING CONNECTIONS 
    • Using a good light source, inspect all disconnected electrical connectors for the following:
      • corrosion - install new connector or terminal and clean the module pins
      • damaged or bent pins - install new terminals or pins
      • pushed-out pins - install new pins as necessary
      • spread terminals - install new terminals as necessary
    • Are the connectors free of corrosion, damaged pins, bent pins, pushed-out pins and spread terminals? 
      Yes No
      Go to  CI18. REPAIR the affected connectors or terminals. REFER to the Connector Repair Procedures wiring diagrams for schematic and connector information.
  18. CI18: CHECK FOR CORRECT IPC OPERATION 
    • Ignition OFF.
    • IPC connector connected. (C220) Make sure the connector seats and latches correctly.
    • Operate the system and determine if the concern is still present.
    • Is the concern still present? 
      Yes No
      INSTALL a new IC.
      CHECK OASIS for any service articles: TSB, GSB, SSM or FSA.
      If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions.
      If no services articles address this concern, INSTALL a new IPC. REFER to the Cruise Control article.
      ORDER a replacement IPC and INCLUDE the RVC on the form.
      If this is a Ford paid repair, INCLUDE the RVC on the warranty claim form.      		 The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.
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