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Pinpoint Test D: The Brake Transmission Shift Interlock (BTSI) System Does Not Operate Properly

  1. Normal Operation and Fault Conditions 

    The brake transmission shift interlock (BTSI) system prevents the selector lever from leaving the park position unless certain conditions are met. To release the brake transmission shift interlock (BTSI), the ignition must be on with the engine running, the brake pedal must be applied, and the selector lever must be pulled toward the driver. When the selector lever is pulled toward the driver and the PCM/ TCM is not commanding the selector lever to be locked, the GSM will unlock the shift detents, allowing the selector lever to move from the park position.

    DTC Fault Trigger Conditions 

    DTC Description Fault Trigger Condition
    GSM P0929:00 Gear Shift Lock Solenoid/Actuator Circuit "A" Range/Performance: No Sub Type Information This DTC indicates the GSM detected a fault in the gear select lock system, such as a motor or position sensor fault, or the GSM saw the selector lever rotate out of a locked state.

    Possible Sources 

    • Brake switch fault
    • Module communication
    • Connectors damaged or pushed-out terminals, corrosion, loose wires and missing or damaged seals
    • GSM

  2. D1 CHECK THE GSM (GEAR SHIFT MODULE) FOR DIAGNOSTIC TROUBLE CODES (DTCS)

    • Using a diagnostic scan tool, retrieve all continuous memory diagnostic trouble codes (CMDTCs) from the GSM.

    Are any system voltage, internal module, or module communication diagnostic trouble codes (DTCs) present? 

    Yes  RESOLVE those diagnostic trouble codes (DTCs) first. REFER to Diagnostic Trouble Code (DTC) Chart 
    No  GO to  D2

  3. D2 CHECK THE OPERATION OF THE BRAKE TRANSMISSION SHIFT INTERLOCK (BTSI) SYSTEM

    • Start the engine.

    • Press the brake pedal.

    • Without pulling on the selector lever, try moving the selector lever out of Park. The selector lever should be locked in the Park position.

    • Release the brake pedal. Pull on the selector lever, then try moving it out of Park. The selector lever should be locked in the Park position.

    • Press the brake pedal, pull on the selector lever, and move the selector lever to all gear positions. The selector lever should move to all gear positions.

    • Select PARK.

    Does the brake transmission shift interlock (BTSI) system operate correctly? 

    Yes  GO to  D4
    No  GO to  D3

  4. D3 CHECK THE OPERATION OF THE BRAKE SWITCH

    • Access the PCM and monitor the BOO1PID

      Access the BCM and monitor the BRK_PDL_SW2PID

    • Press and release the brake pedal while observing PID BOO1 and PID BOO2.

    Does the status of PID BOO1 and PID BOO2 change appropriately as the brake pedal is pressed and released? 

    Yes  GO to  D5
    No  RESOLVE any brake switch diagnostic trouble codes (DTCs) that are present in the PCM or in the BCM. REFER to Diagnostic Trouble Code (DTC) Chart 

  5. D4 CHECK THE GSM (GEAR SHIFT MODULE) FOR DIAGNOSTIC TROUBLE CODES (DTCS)

    NOTE: If a GSM self-test is carried out, the driver door must be fully closed. A false P166B DTC may set if the driver door is not fully closed during the self-test.

    • Using a diagnostic scan tool, clear all GSM diagnostic trouble codes (DTCs).

    • Ignition OFF.

    • Start the engine.

    • Repeat the following steps 3 times, waiting at least 15 seconds between each repeat:

      • Press and hold the brake pedal.

      • Select Drive.

      • Select Park.

      • Release the brake pedal.

      • With the brake pedal released, attempt to move the selector lever out of the Park position.

    • Using a diagnostic scan tool, CARRY OUT the GSM self-test.

    Is DTC P0929 present? 

    Yes  GO to  D5
    No  The system is operating correctly at this time. The concern may have been caused by an intermittent fault condition.

  6. D5 CHECK FOR CORRECT GSM (GEAR SHIFT MODULE) OPERATION

    • Ignition OFF.

    • Disconnect and inspect the GSM connector.

    • 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

    • Connect the GSM connector. Make sure it seats and latches correctly.

    • Operate the system and determine if the concern is still present.

    Is the concern still present? 

    Yes  CHECK for an applicable TSB, GSB, SSM, or FSA. If a service bulletin exists for this concern, discontinue this test and follow bulletin instructions. If none address this concern, INSTALL a new GSM. REFER to: Gear Shift Module (GSM) - Vehicles With: Column Shift .
    No  The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.
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