Damaged, chafed or corroded wiring in the sensor signal, supply or ground circuit; Poor connection at the sensor or control unit connector, such as corrosion, bent pins or water ingress; Faulty rough road sensor (where fitted as a separate unit); Wheel speed sensor or ABS/ESP module fault supplying the rough road signal over the network; Loose or incorrectly mounted sensor, or damage from impact or previous repair work; Fault in the engine control unit or outdated software that misreads the signal.

P0318

Rough Road Sensor A Signal Circuit.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
18: FaultThe specific fault in that area

What it means

P0318 is the generic SAE J2012 code for a fault in the Rough Road Sensor A signal circuit. The rough road sensor, which may be a dedicated sensor or derived from wheel speed or accelerometer data depending on the vehicle, tells the engine control unit when the car is on a bumpy surface. The control unit set the code because the signal was missing, stuck, out of range or implausible compared with other inputs such as wheel speed.

Symptoms

Engine warning light on
Traction control or ABS warning light on at the same time on some vehicles
False misfire codes set when driving on uneven roads
Misfire monitoring suspended or unreliable on rough surfaces
Occasional rough running or hesitation on bumpy roads
No noticeable symptoms other than the warning light

Possible causes

Damaged, chafed or corroded wiring in the sensor signal, supply or ground circuitlikely
Poor connection at the sensor or control unit connector, such as corrosion, bent pins or water ingresslikely
Faulty rough road sensor (where fitted as a separate unit)possible
Wheel speed sensor or ABS/ESP module fault supplying the rough road signal over the networkpossible
Loose or incorrectly mounted sensor, or damage from impact or previous repair workpossible
Fault in the engine control unit or outdated software that misreads the signalrare

How to diagnose

Read all stored codes and freeze frame data, noting any ABS, traction control or wheel speed codes alongside P0318
Check for related technical service information for the specific model, as the sensor type and location vary by manufacturer and engine
Visually inspect the sensor, its mounting and the wiring harness for chafing, damage, corrosion or water ingress
Disconnect and inspect the connectors at the sensor and control unit for bent, loose or corroded terminals
Check live data for the rough road signal and wheel speeds, comparing readings when stationary and on a smooth road drive
Test the sensor supply voltage, ground and signal wiring for continuity, short circuits and resistance against the manufacturer's specification
Test or substitute the sensor only after the wiring and connectors are proven good
Clear the code and road test, including a rough surface, to confirm the fault does not return

How to fix

Repair or replace damaged wiring and restore the correct circuit continuity
Clean, repair or replace corroded or damaged connectors and terminals
Replace the rough road sensor if it fails testing, and secure it to the correct mounting torque
Repair any wheel speed sensor or ABS/ESP fault that feeds the rough road signal
Update or reprogram the control unit software only if the manufacturer lists an outdated calibration as a known cause

Can I keep driving?

Low severity

The car can normally be driven, as the main effect is reduced misfire monitoring on rough roads. Book it in soon, especially if traction or ABS warning lights are also on, since those systems may be affected.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.