Edmunds Answers



  • MrShift@Edmunds 07/18/11 10:30 pm PST

    The automatic transmission shift lock control system is a safety device that prevents an inadvertent shift out of PARK when the engine is running. The driver must press the brake pedal before moving the shift lever out of the PARK position. The system consists of the following components:

    • The automatic transmission shift lock control solenoid
    • The body control module (BCM)
    • The engine control module (ECM)

    The BCM controls the voltage to the supply circuit of the shift lock control solenoid. The following conditions must be met before the BCM will supply voltage to the shift lock control solenoid:

    • The ignition is in the ON position.
    • The ECM sends an input via GMLAN serial data to the BCM indicating the transmission is in the PARK position.
    • The BCM determines the brake pedal is applied according to the brake pedal position sensor.

    Since the shift lock control solenoid is permanently grounded, the BCM supplies voltage to the automatic transmission shift lock control solenoid, mechanically unlocking the shift lever allowing the driver to move the shift lever out of the PARK position as the solenoid energizes. When the brake pedal is not applied, the BCM turns the control voltage output of the shift lock control solenoid OFF, de-energizing the shift lock control solenoid. The de-energized solenoid mechanically locks the shift lever in the PARK position.

  • docj 07/18/11 11:13 pm PST

    Just to add..if the Battery goes dead the vehcile obviously wont start but the key will also not come out of the ignition and you wont be able to shift it out of park.

    So have the battery tested....

    Doc J

  • Stever@Edmunds 07/19/11 11:43 am PST

    You can reply in this thread by clicking the Answer this Question button and that will help keep all the information in one spot. Thanks!

  • aev2 07/20/11 5:49 pm PST

    It ended up being the battery. Although the voltage was fine, it didn't have the cranking amps needed. New battery, and all is well again. Thanks all!

  • MrShift@Edmunds 07/20/11 9:04 pm PST

    Well there you go. Car computers tend to go nuts if they don't get a precise range of voltage. Glad to hear you're on the road again.


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