Cause
Faulty rough road sensor
The sensor telling the module the road surface is rough, faulty so the module cannot distinguish surface-induced crankshaft speed variation from a genuine misfire. Misfire detection works by measuring tiny fluctuations in crankshaft speed, and a rough road shakes the driveline enough to produce fluctuations that look exactly like one.
So the sensor exists to suppress false misfire reports, and losing it costs accuracy in both directions. Without a trustworthy signal the module either disables misfire monitoring — so a real misfire goes unreported and the converter is unprotected — or reports misfires the engine is not having. False misfire codes that appear only on poor surfaces are this sensor, and the correlation with road conditions is the diagnostic clue.
Not every vehicle has a dedicated sensor; many derive the same information from the braking module's wheel speeds, which is why these codes often accompany a communication fault rather than a sensor fault. Establish which arrangement the vehicle uses before looking for a part — on a derived system there is no rough road sensor to replace, and the fault is in the data path.
Typically a moderate job.
Codes this can cause (3)
Codes where this is a likely explanation first, rather than merely a possible one.
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Others who found this
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about Faulty rough road sensor.