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P0318 – Rough Road Sensor A Signal Circuit (OBD2)

P0318 means "Rough Road Sensor A Signal Circuit". The control unit has detected a fault in the electrical circuit of the rough road detection / crankshaft variation learn: the signal or control current is missing or outside the expected window. The code does not say whether the value is too high or too low, so the wiring and the component itself both have to be checked.

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P0318 quick summary

Fault codeP0318
MeaningRough Road Sensor A Signal Circuit
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityLow
Can I drive?Yes. The engine runs normally, but misfire monitoring may be limited and the car may fail an emissions inspection.
Repair cost€0 – €250

Why rough road detection matters for misfire monitoring

These codes relate to the systems that prevent false misfire detection: rough road sensors and the learned crankshaft variation.

Misfire detection relies on tiny changes in crankshaft speed. Driving on a rough road or production tolerances of the reluctor ring can cause similar changes. To avoid false misfire codes, some vehicles use a rough road sensor (or wheel speed data) and all modern engines learn the crankshaft reluctor's variation.

P0315 means the crankshaft position system variation has not been learned – typically after replacing the control unit, crankshaft sensor or reluctor ring. P0317–P0319 cover rough road hardware and sensors.

These codes do not mean the engine is misfiring, but misfire monitoring may be disabled until the issue is fixed.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 16702 (P0318). Both numbers mean the same fault.

Symptoms of P0318

  • Check Engine light on
  • Misfire monitor not ready
  • Usually no driving symptoms
  • Code after replacing the control unit or crankshaft sensor

Most common causes of P0318 (most likely first)

Mechanic's Pro Tip

Always run the crankshaft variation relearn after replacing an engine control unit or crankshaft sensor on vehicles that require it – otherwise false misfire codes can appear.

  1. 1.Damaged wire or loose, corroded connector at the rough road detection / crankshaft variation learn

    Most likely

    Green or white corrosion, pushed-back pins and chafed insulation near hot or moving parts are the most common findings.

  2. 2.Faulty rough road detection / crankshaft variation learn

    An internal break or short in the component itself.

  3. 3.Blown fuse or missing supply voltage

    If several codes appeared at the same time, check the shared fuse, relay or ground point first.

  4. 4.Crankshaft variation relearn not performed

  5. 5.Control unit or crankshaft sensor replaced

  6. 6.Rough road sensor or wiring fault

  7. 7.ABS wheel speed data missing (if used for rough road detection)

Step-by-step diagnostic guide

  1. 1

    Read codes

    Read all codes and check whether parts were replaced recently.

  2. 2

    Check the circuit with a multimeter

    With the ignition off, unplug the rough road detection / crankshaft variation learn and the control unit connector (or back-probe), then check each wire between them for continuity and for shorts to ground and to battery voltage. Compare the component's resistance or supply voltage with the value in the repair manual.

    Multimeter: Wire continuity: below about 1 Ω. Wire to ground with both connectors unplugged: no continuity. Supply/reference with ignition on: usually 5 V for sensors, battery voltage for actuators.

  3. 3

    Perform the crankshaft variation relearn

    Run the crankshaft position variation learn procedure with a scan tool (often requires a warm engine and defined rpm).

  4. 4

    Check the rough road sensor

    Where fitted, check the sensor supply, ground and signal.

  5. 5

    Check ABS data

    Check for ABS codes if the rough road signal comes from wheel speeds.

  6. 6

    Clear and verify

    Clear codes and verify that the misfire monitor completes.

Frequently asked questions

Can I keep driving with P0318?

Yes. The engine runs normally, but misfire monitoring may be limited and the car may fail an emissions inspection.

How much does it cost to fix P0318?

Typical repair costs are 0 € – 250 €, depending on the cause and the vehicle. The most common fixes are: damaged wire or loose, corroded connector at the rough road detection / crankshaft variation learn; faulty rough road detection / crankshaft variation learn; blown fuse or missing supply voltage. Always confirm the cause with the tests above before buying parts.

Does P0315 mean my engine misfires?

No. It means the control unit has not learned the crankshaft variation, so misfire detection may be limited.

How is the relearn done?

With a scan tool procedure, usually with a warm engine and a defined engine speed.

What is the difference between P0318 and similar codes?

P0318 belongs to a group of codes for the same component that differ in the type or location of the fault: P0317 – Rough Road Hardware Not Present; P0319 – Rough Road Sensor B Signal Circuit. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.