Engine

P0318 — Rough Road Sensor 'A' Signal Circuit Fault

Severity: low Safe to drive

What P0318 means

The engine control module detected an incorrect or implausible signal in the Rough Road Sensor 'A' circuit. This signal tells the computer when the car is shaking from a bumpy surface, so it does not mistake road vibration for engine misfires. When the circuit is faulty, the rough road data can no longer be trusted.

Symptoms

  • Check Engine light on
  • Intermittent ABS or traction control warnings
  • False misfire codes on rough roads
  • Rough idle
  • Possible hesitation under load

Possible causes

  1. Damaged sensor wiring (open, chafed or shorted)
  2. Corroded or loose connector terminals
  3. Faulty rough road sensor or accelerometer
  4. Communication problem with the ABS module or another unit supplying the signal
  5. Failed engine control module (rare)

How to diagnose

  1. Scan all modules and review freeze frame data, noting any ABS or misfire codes (P0300-P030x)
  2. Look up the wiring diagram to find the sensor 'A' location or signal source for this vehicle
  3. Inspect the harness and connector for rubbing, moisture, corrosion and poor retention
  4. Test power, ground and signal wires with a multimeter for opens and shorts
  5. Watch the sensor signal live on a scan tool while tapping the body or driving
  6. Check network communication and the ABS module's operation
  7. Clear the code and road test to confirm it does not return

Common fixes

  • Repair damaged wiring and clean or replace the connector
  • Replace the faulty rough road sensor or accelerometer
  • Repair the ABS module or network fault
  • Update software or replace the control module if an internal fault is confirmed

Questions and answers

Can I drive with a P0318 code?

Usually yes, because the engine keeps running normally. However, you may see false misfire detection and less precise ABS behavior on rough roads, so get it diagnosed soon.

What is a rough road sensor?

It is a sensor that detects vibration and jolts from the road surface. It helps the computer tell road shake apart from real engine misfires.

Why does P0318 show up with ABS codes?

On many vehicles the rough road signal comes from the wheel speed sensors or the ABS module. A fault in that system or in the link between modules can set both codes.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.