P0318 Rough Road Sensor A Signal Circuit

P0318 points to a signal circuit problem for Rough Road Sensor A. The controller is seeing an electrical or signal issue in the input used to recognize rough-road vibration.

Code details

Generic OBD-II · P0

System: Ignition / Misfire
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not diagnose every misfire event as engine related until the rough-road input and ABS data are known to be believable.

Symptoms of P0318

Rough idle, shaking, or a stumble under acceleration.
A flashing check-engine light during an active misfire.
Power loss and higher fuel consumption.

Common causes of P0318

Worn spark plugs, ignition coils, or plug wires.
Fuel-delivery problems — injectors, pressure, or a lean/rich mixture.
Vacuum leaks, low compression, or a mechanical fault in that cylinder.

Useful checks before replacing parts

Review Rough Road Sensor A data, freeze-frame speed, wheel speed signals, ABS faults, and misfire monitor conditions when the code set.
Inspect sensor power, ground, signal wiring, connector tension, corrosion, mounting, harness routing, and damage near suspension or underbody areas.
Compare the sensor signal with road conditions and check for dropouts, stuck values, or implausible changes during a controlled road test.

Related OBD-II codes

These nearby ignition / misfire entries can help compare wording and pin down the fault area.