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.
Ignition Signal
When ignition is turned to OFF, ON or START position, the TCM checks the incoming voltage. If voltage is less than 8 volts or greater than 26 volts, TCM will cause transmission to enter limp-in mode to prevent damage to electrical components.
When ignition is turned on, TCM performs a series of circuit and relay checks. If no problem is present, TCM provides voltage to transmission control relay, causing contacts to close which supplies voltage to solenoid assembly and TCM. Voltage supplied to TCM is referred to as switched battery voltage. If a problem is present, TCM turns off power supply to transmission control relay, which causes transmission to enter limp-in mode.
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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.