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 Switch Position Run (ISP-R)
The ISP-R provides the PCM with a VBAT input signal from the ignition switch, indicating that the ignition is in either the ON or START position. When the operator turns the ignition to the OFF or ACC position, the internal combustion engine immediately ceases to provide power. The PCM coordinates the power down sequence by controlling the VPWR circuit and issuing the correct commands to shut down the electrical system in an orderly fashion. For additional information, refer to the Normal Power Down Sequence in HYBRID ELECTRIC CONTROL SOFTWARE . The PCM maintains power to the TCM through the VPWR until the power down sequence is complete. The TBCM is always powered directly from the low voltage battery which permits wake-up when the vehicle is off.
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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.