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 Messages
Modules that depend exclusively on serial data messages for power modes stay in state dictated by last valid BCM message until they can check for engine run flag status on serial data circuits. If BCM fails, modules monitor serial data circuit for engine run flag serial data. If engine run flag serial data is true, indicating that engine is running, modules fail-safe to RUN. In this state modules and their subsystems can support all operator requirements. If engine run flag serial data is false, indicating that engine is not running, modules fail-safe to OFF (awake). In this state modules are constantly checking for a change status message on serial data circuits and can respond to both local inputs and serial data inputs from other modules on vehicle.
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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.