P0318
Fix within 1-2 weeksThe engine computer isn't receiving a proper signal from the rough road sensor, which is crucial for accurate misfire detection.
Code P0318 means your engine computer isn't getting a proper signal from the rough road sensor, which helps it detect misfires. Common causes: Faulty sensor (70%), wiring issues (25%). Drivability: Yes, safe to drive, but fix within 1-2 weeks. Repair cost: $100-$300 DIY, $200-$600 professional.
Can I Drive With P0318?
Yes, safe to drive
No restrictions, but fix within 1-2 weeks to prevent further issues.
Stop driving immediately if: Flashing CEL (indicates active misfire), significant power loss, or any unusual engine noises.
Symptoms of P0318
- 1Check Engine Light is on
- 2No noticeable driving issues (most common)
- 3Engine misfires (if actual misfires are occurring and not being properly detected/filtered)
- 4Rough idle or hesitation (less common, but possible if misfires are present)
Common Causes of P0318
Parts most likely causing this code, ranked by probability
The sensor itself has failed internally, sending an incorrect or no signal to the Powertrain Control Module (PCM).
70% of P0318 cases are fixed by replacing this part
Damaged wires, corroded pins, or a loose connection in the rough road sensor circuit prevent the signal from reaching the PCM correctly.
25% of P0318 cases are fixed by repairing wiring or connectors
A rare internal fault within the PCM prevents it from correctly processing the rough road sensor signal.
5% of P0318 cases are fixed by replacing the PCM
Check These First (Before Buying Parts)
- Visually inspect the rough road sensor's electrical connector and wiring for any signs of damage, corrosion, or loose connections. Ensure the connector is fully seated.
How to Diagnose P0318
- 1Visually inspect the rough road sensor and its wiring harness for any obvious damage, corrosion, or loose connections.
- 2Use a scan tool to check for rough road sensor data parameters and ensure the signal changes when the vehicle is driven over varying road surfaces.
- 3Test the rough road sensor's resistance or voltage output with a multimeter, comparing readings to manufacturer specifications.
- 4If the sensor and wiring check out, perform a thorough diagnostic on the PCM, though this is a rare cause.
P0318 on Popular Vehicles
Ford F-150
2004-2024Many F-150s use the ABS wheel speed sensors and ABS module for rough road detection. A P0318 can indicate an issue with these components or their wiring, rather than a dedicated sensor.
60% fixed by addressing ABS system components
Chevrolet Silverado
2007-2024Some Silverado models have a dedicated rough road sensor, often mounted on the frame or firewall. Locating and inspecting this specific sensor and its harness is key.
75% fixed by replacing the dedicated rough road sensor
Honda Accord
2003-2024Honda vehicles often integrate rough road detection into the ABS/VSA module or use accelerometers within the SRS system. Diagnosis requires checking these modules and their associated wiring.
65% fixed by addressing ABS/VSA module or wiring
Frequently Asked Questions
What does P0318 mean?
P0318 indicates that your vehicle's engine computer (PCM) is not receiving a valid signal from the rough road sensor. This sensor helps the PCM distinguish between actual engine misfires and vibrations caused by driving on uneven roads.
Can I drive with P0318?
Yes, safe to drive, but you should fix it within 1-2 weeks. The primary concern is that your engine's misfire detection system is compromised, which can lead to undetected misfires and potential damage to your catalytic converter over time.
Will P0318 clear itself?
No, P0318 will not clear itself. The underlying issue with the rough road sensor circuit needs to be diagnosed and repaired. Once the repair is complete, you will need to clear the code with an OBD-II scan tool.
How do I fix P0318 myself?
Start by visually inspecting the rough road sensor and its wiring for damage. If the wiring looks good, you can test the sensor's output with a multimeter or scan tool. If the sensor is faulty, replacing it is often a straightforward DIY task. If it's wiring, you'll need to repair the damaged section.
How much does it cost to fix P0318?
DIY repair costs for P0318 typically range from $100-$300, primarily for a new rough road sensor. Professional shop repairs usually cost between $200-$600, including parts and labor.
P0318 keeps coming back - why?
If P0318 keeps returning, it points to an incomplete or incorrect diagnosis. Common reasons include: a faulty sensor that was replaced with another faulty one, an intermittent wiring issue that wasn't fully resolved, or a rare PCM issue that was overlooked.
Will P0318 fail emissions/smog test?
Yes, P0318 will cause your vehicle to fail an emissions or smog test. A Check Engine Light (CEL) illuminated for any reason is an automatic failure in states with such inspections.
What's the difference between P0318 and P0300?
P0318 indicates a problem with the rough road sensor circuit itself, meaning the PCM can't properly filter out road vibrations from actual misfires. P0300 (Random/Multiple Cylinder Misfire Detected) means the PCM *is* detecting misfires but can't pinpoint a specific cylinder or the misfires are occurring randomly across cylinders. A P0318 can sometimes prevent the PCM from accurately setting P0300 or other misfire codes.
P0318 on Ford F-150?
On many Ford F-150 models, the rough road detection function is often integrated into the ABS module, using wheel speed sensor data. If you have a P0318 on an F-150, you'll need to check the ABS module and its related wiring, as well as the wheel speed sensors, as a fault in these components can trigger this code.
Questions to Ask Your Mechanic
Did you check the rough road sensor's live data with a scan tool while driving?
Good answer: Yes, I monitored the sensor's output and it showed a flat line or erratic readings, indicating a fault. Or, I saw it working correctly, so I moved on to wiring checks.
What did you find when you inspected the wiring harness to the rough road sensor?
Good answer: I found a corroded connector pin, or a section of frayed wire near the sensor, which I repaired. Or, the wiring looked perfect, so the sensor itself is the likely culprit.
Repair Cost Estimate
DIY Repair
Parts only
$100-$300
Shop Repair
Parts + labor
$200-$600
Save $100-$300 by doing it yourself
Difficulty
intermediate
Time
1-3 hours
Intermediate - requires a scan tool for proper diagnosis and potentially a multimeter, but the physical replacement of the sensor is often straightforward.
Cost of Waiting
Ignoring P0318 means your engine's misfire detection system is compromised. If actual misfires occur, the PCM might not detect them, allowing unburned fuel to enter and severely damage your catalytic converter. A $100-$300 sensor fix now prevents a $1,200-$2,500 catalytic converter replacement later.
While You're In There...
On many vehicles, the rough road detection system relies on ABS wheel speed sensor data. If you're diagnosing P0318 and the sensor is integrated, checking these sensors for proper function is a good idea.
Tools You'll Need
- OBD-II Scan Tool
- Multimeter
- Basic hand tools (sockets, wrenches)
- Wire strippers/crimpers (if wiring repair is needed)
P0318 is a sensor circuit code, not an immediate engine failure. Most repairs involve replacing a relatively inexpensive sensor or fixing a simple wiring issue, restoring your engine's critical misfire detection system.
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Your Next Steps
Step 1: Visually inspect the rough road sensor and its wiring harness. Look for any frayed wires, melted insulation, or corroded connectors. Ensure the connector is securely attached.
Step 2: If the visual inspection doesn't reveal any issues, use an OBD-II scan tool to monitor the rough road sensor's live data. Drive the vehicle over a bumpy road and observe if the sensor's readings change as expected. If the readings are flat or erratic, the sensor is likely faulty.
Step 3: If the sensor's live data is suspicious, or if your vehicle uses a dedicated rough road sensor, test the sensor directly with a multimeter for resistance or voltage output according to your vehicle's service manual. If it fails, replace the sensor. If the sensor tests good, focus on tracing and testing the wiring for continuity and shorts. Parts you'll likely need: a new rough road sensor (if applicable to your vehicle).