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.
Circuit/System Description
The transmission range (TR) switch is an integral part of the transmission control module (TCM). As the gear range selector lever is moved, the state of the Starter Inhibit Circuit may change, causing the circuit to open or close. An open circuit indicates a drive range and a low voltage signal, 0 volts, at the engine control module (ECM). A closed circuit indicates PARK or NEUTRAL and a high voltage, 12 volts, signal at the ECM.
The ECM uses the Starter Inhibit circuit status from the TCM in order to enable starter operation.
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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.