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.
Rough Road Detection
The misfire monitor may include a rough road detection system to eliminate false misfire indications due to rough road conditions. The rough road detection system uses data from the antilock brake system (ABS) wheel speed sensors for estimating the severity of rough road conditions. This is a more direct measurement of rough road over other methods which are based on driveline feedback via crankshaft velocity measurements. It improves accuracy over these other methods since it eliminates interactions with actual misfire.
In the event of an rough road detection system failure, the rough road detection output is ignored and the misfire monitor remains active. An rough road detection system failure could be caused by a failure in any of the input signals to the algorithm. This includes the ABS wheel speed sensors, brake pedal sensor, or controller area network (CAN) bus hardware failures. Specific DTCs indicate the source of these component failures.
A redundant check is also carried out on the rough road detection system to verify it is not stuck high due to other unforeseen causes. If the rough road detection system indicates rough road during low vehicle speed conditions where it is not expected, the rough road detection output is ignored and the misfire monitor remains active.
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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.