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P0318 OBD-II Trouble Code: Rough Road Sensor A Signal Circuit

Check Engine Light

What the P0318 code means

The powertrain control module (PCM) has noticed a change in your crankshaft position. This tells your car that you are experiencing uneven or rough driving.

What causes the P0318 code?

Any time the PCM recognizes a sudden crankshaft position fluctuation while driving on uneven or rough surfaces, a code of this type may be stored and the service engine soon lamp will come on. Please note that some vehicles require several failure cycles until the service engine soon lamp comes on. You might also have disconnected, missing, or defective rough road sensors or other rough road detection hardware.

What are the symptoms of the P0318 code?

Symptoms may include a misfiring engine or hesitation followed by a stored trouble code and a Check Engine light that won’t turn off. You may also find that your traction control or antilock brake systems are also affected.

How does a mechanic diagnose the P0318 code?

You should start your diagnosis with a careful visual inspection of all rough road sensors, electrical connectors, wiring harnesses, and hardware. Always repair or replace any defective components, or any disconnected or damaged wiring or connectors. If the wiring connectors, harnesses, and hardware on the rough road sensor system seem to be in good shape, then connect your scanner and record all freeze frame data and stored trouble codes. Remember to always diagnose and repair codes in the order in which they are stored.

If your problem persists, inspect connector faces for debris, dirt, and corrosion, and then replace or repair wiring, components, and connectors if they are in poor shape. Using your digital volt/ohmmeter, test the ground signals and voltage at the sensor connector. If both the voltage and ground signals are present, then reconnect your sensor and test the signal wire at the connector while recreating a rough road condition. If the sensor is showing it has power and ground but provides no signal voltage or the signal voltage fails to change with your changing conditions, you know you need to replace the sensor.

However, if everything checks out, then you may have a faulty control module. But please note that an experienced technician with a specialized scanner may be able to determine the exact malfunction more easily than someone with a digital volt ohmmeter and code reader. To diagnose a P0318 using your digital volt ohmmeter would involve probing thousands of circuits, which is obviously time consuming and tedious. Additionally, one misplaced probe could destroy your expensive control modules and require that the vehicle be reprogrammed.

Common mistakes when diagnosing the P0318 code

A common mistake is to replace your wheel speed sensors, crankshaft position sensors, and camshaft. This will not necessarily solve the problem. This is why it is so important to use the proper diagnostic equipment, or to take your vehicle to a professional technician who will diagnose the problem for you.

How serious is a P0318

Because this problem can affect your brakes, it should be treated very seriously. As soon as you see this code, either take your vehicle into a professional technician, or begin doing research to fix the problem yourself.

What repairs can fix the P0318 code?

You or your professional technician may need to replace your rough road sensor. However, this can be determined only after careful and thorough inspection. A P0318 code is probably best left to a professional technician, because he or she will have the tools to properly diagnose the problem.

Additional comments for consideration regarding the P0318 code

A P0318 can become complicated and may require that you probe thousands of circuits independently in order to determine the exact problem. Obviously, this may become a complicated and involved task even for the most experienced technician. Therefore, it is important to do the proper amount of research before you begin to work. A mistake on your part could result in your having to reprogram the entire vehicle. If you are thinking of doing this yourself, do not hesitate to contact a professional technician to ask questions about the best way to solve your problem.

Need help with a P0318 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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