Check Engine Code P0340

What are the causes of check engine light code P0340 and how do I fix it? Find out the answer to both questions from a certified mechanic.

This is a fairly common fault code. Your vehicles computer (PCM, ECM, etc.) uses the CMP (camshaft position sensor) to figure out what it should set the timing at. This is a very important thing because without knowing what the timing should be the computer is useless.

This code basically means that the computer has sent (or thinks it has) a signal to the camshaft position sensor, but it does not see the correct signal being returned from the sensor. Some symptoms that you might have noticed from this code are hard starting, loss of power, engine popping noises, misfires, check engine light etc.

What Causes the P0340 Code?

  • Camshaft Position Sensor
  • Wiring Problem

Less Common Causes

  • The Computer
  • The Reluctor Wheel on the Camshaft

To troubleshoot, repair and maintain your vehicle, you'll need diagnostic and repair information that is specific to your car or truck. For this I personally use and recommend ALLDATAdiy. With full manuals for over 30,000 vehicles online, you will find an exact match for your vehicle's year, make and model.

Besides being cheaper than a factory manual, they also offer step by step repair instructions and detailed diagrams beyond what is found in most printed manuals. Click here for a sample of their diagnostic and repair information.

How to Fix Engine Code P0340

The first thing you need to check is all of the wiring you can see. Start with the battery cable connections make sure they are clean and tight. This might seem like a dumb thing to do, but if the computer does not get a steady feed of electricity from the battery it can cause all kinds of problems.

Check for any wires that might have rubbed through or any connectors that might be loose or have come disconnected. Check the fuse box in the vehicle and the relay center under the hood. Make sure the fuses are good and there is no melted plastic, indicating a fire. These are the main wiring problems you are looking for.

If you have checked all of the obvious things and still can't find the solution,  then you have to start suspecting either the sensor or the computer.

Camshaft position sensors go bad a lot more than PCM's do so I would suspect that first. Unfortunately there is no easy way for you to test it. It will take some expensive test equipment and a skilled technician to test the sensor itself.

If you are a risk taker, you can just buy the CMP sensor and install it. It might fix the problem but there is no guarantee without properly diagnosing it.

If you still have any unresolved vehicle problems or questions, you can ask an auto mechanic online. For expert answers specific to your vehicle's make and model, I recommend JustAnswer Car. They have a large pool of certified mechanics to answer your questions for a small fee and you can also browse their answers to other users for free.

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