Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Automatic Transmission Shift Lock Control System
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 gearshift lever out of the Park position. The system consists of the following components:
- The automatic transmission (A/T) shift lock control actuator (integrated into the shift control assembly).
- The automatic transmission (A/T) shift lock control switch (part of stoplamp switch).
With the ignition switch in the ON position, voltage is supplied to stoplamp switch. Voltage flows through the normally closed contacts of the stoplamp switch to the A/T shift lock actuator. When actuator is grounded, this energizes the A/T shift lock actuator causing the transmission gearshift lever to be physically locked in the Park position. When the brake pedal is pressed the contacts in the stoplamp switch open, de-energizing the A/T shift lock actuator. This allows the gearshift lever to be moved out of the Park position.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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