OBD2 Trouble Code P0340

OBD2 Trouble Code P0340

Your car’s engine has a lot of sensors, and whenever something doesn’t seem right with one of them the computer will generate a fault code. Fortunately these sensor failures are usually easy issues to fix.

What Does P0340 – “Camshaft Position Sensor Circuit Malfunction” Mean?

The camshaft position sensor is one of the many sensors connected to your engine’s computer that helps it calculate the most efficient parameters for your engine. A circuit malfunction simply means that the sensor’s data is not reaching the computer.

It doesn’t mean that the sensor has gone bad, although that is one possibility. Often, it’s a simple case of a loose wire or corrosion. The most difficult part of diagnosing a cam position sensor issue is that you may not have any symptoms other than an illuminated check engine light due to the stored fault code. That will cause you to fail inspection but may otherwise cause no issue with normal driving.

How Serious Is Code P0340?

The seriousness of this code depends on what part of the circuit has failed and when it failed. In general, the symptoms will worsen as time goes on, resulting in expensive mechanical issues if left untreated. The sooner you notice the problem and get it repaired, the better.

Stop Driving

  • If the check engine light begins flashing
  • If you notice the car is having a lot of difficulty running
  • If you hear knocking or other loud noises

Camshaft Position Sensor

The camshaft position sensor is located near the timing gears or pulleys and measures the speed of the camshaft. The engine’s computer (ECU/PCM) will then use that information to calculate what degree of rotation the camshaft is at, known as the cam position.


  • Check Engine Light is Illuminated
  • Occasional pinging
  • Occasional engine performance issues
  • Issues starting
  • Car fails inspection


There are four main causes of a cam sensor circuit fault. Any number of these causes can lead to this code, so it’s important to check them all before coming to any conclusions.

There Is Damaged Wiring or Loose Connections

This is the most common issue. The cam sensor is usually in a spot that gets very hot and is exposed to the elements. Rodents love to chew on wires that are exposed, and the heat makes the wires brittle.

The Position Sensor Has Failed

This is the second most common issue. Sensors are considered wear items. It’s common to see manuals recommend replacing them prior to the 100k mile mark and when this happens your computer will display a code.

The Computer Is Malfunctioning

This issue is somewhat rare but not unheard of. If the PCM/ECU/ECM is having a problem, it can display any number of faults. In this case, it might not have anything to do with your vehicle’s camshaft position sensor.

Internal Timing Parts Have Failed

This issue is the rarest unless you have recently done work on your car. There are a variety of internal parts that can break or be installed improperly that affect engine timing. If the engine timing is off, it can be interpreted by the computer as a fault.


The following steps start out easy and may only require simple tools. As they progress, they get more complicated and may require specialized tools, so don’t feel like you need to perform every step. Stop when you don’t feel comfortable and take the car to a mechanic. Usually, fixing a sensor is a fairly inexpensive trip to a shop.

  1. Locate the sensor using a shop manual or Google, and then visually inspect the wires connected to it. If you find a loose or broken wire, your journey is over. Repair the wire, and you should be good.
  2. If the wires look good, replace the sensor. They don’t cost very much, and they are usually very easy to get to. You may not even need any tools; just unplug the old one and plug a new one in.
  3. After you replace the sensor and the problem persists, you should run a more comprehensive test on the wires. Check to make sure the sensor is getting the correct voltage, and check continuity from the sensor to the computer.
  4. If the problem still persists, you may need to run a more advanced diagnostic on your car’s CPU. A more advanced OBD2 scanner can sometimes diagnose a PCM issue. Otherwise, remove the computer and bring it to a shop that can test it.
  5. Tear down the engine to look for broken or loose parts. If you are at this step, be sure to check the sensor reluctor wheel. It’s a common fail point, and it’s easy to put on incorrectly after working on the top end.

We hope this guide can get you back on the road fast. Just remember two things. One, even if the computer says the sensor has failed, it might just be a bad wire. And two, go with your gut when driving a car. If it feels like the engine is in bad shape, it probably is, and you shouldn’t be driving the car.

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