P0318
Rough Road Sensor A Signal Circuit
Misfire detection (rough-road input)
Generic OBD-II
High
What it means
P0318 means the ECM has a problem with the "A" rough-road sensor signal. This sensor tells the engine computer when you're driving over bumps so it doesn't mistake road-induced crankshaft speed changes for an engine misfire. The car drives normally, but the misfire diagnostic may be paused until the circuit is repaired.
High
Can I keep driving? The car itself drives normally — this is an input-circuit fault — but the ECM may suspend the misfire monitor, so it's worth fixing so a real misfire isn't missed.
Common symptoms
What you'll notice
- Check-engine light on
- Often no noticeable change in how the car drives
- Misfire monitor may not complete (readiness not set)
- Related crankshaft/misfire codes may appear alongside it
Common causes
Most likely first
- Faulty rough-road sensor (or the G-sensor/wheel-speed source it uses)Likely
- Open, shorted, or damaged wiring in the signal circuitCommon
- Loose or corroded connector at the sensor or moduleCommon
- Loss of rough-road data over the vehicle network from the ABS moduleLess often
How to diagnose & fix
Work through it in order
- Scan for other stored codes first — network or ABS faults can trigger this.
- Inspect the rough-road sensor connector and wiring for damage or corrosion.
- Check the signal circuit for continuity and correct reference voltage.
- Confirm the ABS/data source is reporting rough-road information correctly.
- Replace the sensor only after wiring and data-source checks pass. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0318?+
Yes. The rough-road sensor only helps the ECM tell real misfires from bumps in the road, so the car drives normally, but repair it so genuine misfires aren't overlooked.
Can I just clear P0318?+
It will return if the circuit or data source is still faulty. Fix the wiring or sensor first, then clear it.
Related codes
Often seen with P0318
Read & clear P0318 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX