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 Master
On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle the PMM is the body control module (BCM). The PMM receives 4 discrete ignition switch signals to differentiate which power mode will be sent over the Serial Data circuits. The table below illustrates the state of these inputs in correspondence to the ignition switch position and one additional circuit for transmission control:
| Ignition Switch Position | IGN 0/ACCESSORY/RUN/START | IGN 1/RUN/START | IGN 2/ACCESSORY/RUN | IGN 3/RUN | START | Power Mode Transmitted |
|---|---|---|---|---|---|---|
| Off | 0 | 0 | 0 | 0 | 0 | OFF/Awake |
| Start | 1 | 1 | 0 | 0 | 1 | Crank |
| Accessory | 1 | 0 | 1 | 0 | 0 | Accessory |
| Run | 1 | 1 | 1 | 1 | 0 | Run |
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.