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.
Serial Data Power Mode
On vehicles that have several control modules connected by serial data circuits, one module is Power Mode Master (PMM). On this vehicle PMM is Body Control Module (BCM). BCM receives 3 signals/circuits from ignition switch: ACC/RUN/CRANK (ignition 0), RUN/CRANK (ignition 1) and ACC/RUN (accessory).
To determine correct power mode, BCM uses following information:
- State of these signals/circuits, either switch closed (battery voltage = 1) or switch open (open = 0).
- Sequence of switch closures received by BCM.
- Status of engine run flag.
NO RELATED
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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.