What Does P0318 Mean?
There is a malfunction in the Rough Road Sensor A signal circuit. This sensor (typically an accelerometer or uses ABS wheel speed data) helps the PCM distinguish between engine misfires and road-surface-induced vibrations. A faulty signal means the PCM cannot properly filter out rough road conditions, potentially leading to false misfire detections or suppressed real misfire alerts.
Common Causes
30%
Damaged or corroded wiring in the rough road sensor circuit
25%
Failed rough road sensor (accelerometer) with no output or erratic signal
20%
Poor ground connection at the sensor causing signal noise or dropout
15%
ABS module fault preventing rough road data from being calculated from wheel speed inputs
10%
PCM internal fault in the rough road signal processing circuit
Diagnostic Steps
1
Using the scan tool, monitor the Rough Road Sensor A PID while driving over a speed bump or rough surface — the signal should show a clear response to road irregularities.
2
Inspect the rough road sensor wiring from the sensor to the PCM for chafing, corrosion, or broken wires. Pay attention to areas near exhaust heat and suspension components.
3
Check the sensor connector for backed-out pins, corrosion, or water intrusion. Clean with electrical contact cleaner if contamination is found.
4
Measure the sensor supply voltage (typically 5V reference) and ground at the sensor connector with the key on, engine off. If voltage is out of spec, trace the circuit back to the PCM.
5
If the rough road signal is derived from ABS wheel speed sensors, check for ABS DTCs and verify all four wheel speed sensor signals are clean and consistent.
Estimated Repair Cost
$75 - $400
Parts + labor, varies by vehicle and location
There is a malfunction in the Rough Road Sensor A signal circuit. This sensor (typically an accelerometer or uses ABS wheel speed data) helps the PCM distinguish between engine misfires and road-surface-induced vibrations. A faulty signal means the PCM cannot properly filter out rough road condition...
The most common cause of P0318 (Rough Road Sensor A Signal Circuit) is: Damaged or corroded wiring in the rough road sensor circuit
Typical repair costs for P0318 range from $75 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. The vehicle will operate normally, but you may experience false misfire-related DTCs when driving on rough or uneven roads. This code does not affect engine performance or driveability. Repair at your earliest convenience.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0318 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Management / Misfire Detection
Difficulty
Type
Generic (SAE)
Recommended Tools
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