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.
Theory Of Operation
The PCM receives voltage on the dedicated wake-up signal from the BCM to turn on and become active. The wake up signal voltage must be above approximately 5.0 volts for the PCM to recognize it as a valid signal. The wake-up is sent for all of the following reasons:
- The ignition is turned on.
- A refueling event is being requested.
- The Evaporative System diagnostics need to be performed (This occurs six hours after the ignition is turned off).
When the wake-up signal is sent, the BCM will send a corresponding bus message with the reason for the signal to the PCM. If the PCM receives the wake-up signal without one of the above corresponding messages from the BCM, a fault is set.
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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.