camshaft positon sensor

P0340 Camshaft Position Sensor A – Malfunction

In OBD2 Trouble Codes by Magnus Sellén1 Comment

The P0340 error code relates to the camshaft sensor.

Internal combustion engines require the right timing of the air/fuel mixture during ignition. If the timing is wrong then you are going to experience misfires.

Modern cars use the onboard computer to determine the right timing. Camshaft sensors are used to relay information to the PCM for this.

If the sensors are faulty then the PCM receives wrong signals. A car experiencing wrong timing will experience loss of power and can be difficult to start. In addition, the check engine light will come on.

The camshaft positioning sensor will also record the spinning rate of the camshaft and send this information to the PCM. The PCM/ECM will utilize this information to regulate the amount of fuel and the timing of the ignition. This leads to fuel efficiency. The sensors can also identify the positioning of the combustion pistons. A gap between the camshaft passes a magnetic field that affects the sensors. This, in turn, affects the sensors’ voltage.

Causes of Error P0340

  • Faulty wiring from the camshaft to the PCM
  • Faulty camshaft position sensors
  • PCM programming errors
  • Faulty reluctor camshaft wheel
  • Weak battery
  • Short or open camshaft position sensor harness
  • Problems with system circuit

Common symptoms of P0340

  • Engine misfiring
  • Loss of engine power
  • Car stalling
  • Hard start or the car failing to start
  • Check engine light turns on

How to fix P0340

Check wires: The camshaft sensor is connected to the PCM by a series of wires. If these are loose or damaged, there are problems with information transmission. First, check the wiring of your battery and make sure that all connections are tight.  Also, check the ground wire between the engine and the body.

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Check the wires from the sensor(s) to the engine control unit to look for any visible damage.

Camshaft sensors: The most common problem related to the P0340 code is actually broken camshaft sensors.

Sensors on the camshaft collect information and forward it to the PCM. This then influences the timing of air and fuel injection into the combustion chamber. Like any electronic device, if the camshaft sensors are dirty or defective, they can no longer pass on the correct information.

Camshaft reluctor: Check for visible damage to the reluctor wheel on the camshaft from which the camshaft reads the information. This is not a common problem, but if you have already replaced the sensors and made sure that the wires are okay, you ought to check this.

Engine control unit: If the wires, sensor, and camshaft are good, there could be a problem with the hardware or software of your engine control unit. You should really let an experienced diagnostic technician take a look at your ECU. You can read the signal from the camshaft sensor with an oscilloscope, but that requires a lot of knowledge.

Can drive with an error P0340?

Error P0340 is associated with a malfunctioning camshaft position sensor. The sensor plays a vital role in detecting the rotational speed of the camshaft and relaying this information to the PCM.

The PCM then determines the opening and closing of the intake valves. It will also determine the right timing for ignition. When you have an error P0340 problem, your engine will misfire or the car can stall while driving. Depending on the car, you might have problems driving or starting your car and it’s recommended to fix the problem as fast as possible.

Diagnosing error P0340

If you want to retrieve the error codes stored in the PCM, you must use an OBD2 scanner. Most problems with error P0340 are related to the camshaft wiring and sensors. First, examine the wiring from the camshaft sensor to the PCM and check for corrosion or loose wires.

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Next, check the camshaft position sensor for damage. Sensors start to fail if they are corroded by dirt. You can clean them with a special sensor cleaning spray. Spray the sensors and then allow them to dry before you install them again.

It is also good to check that the sensors receive the correct voltage. This requires a scan tool or an oscilloscope to read. If the readings are above the recommended values, you must replace the sensors. If everything is fine or has been replaced, but you still have error P0340, the problem may be with the PCM itself. Like most computer elements, the PCM has been programmed to do its job. But over time, the system develops error codes that can only be corrected by reprogramming the unit.

If the problem is not addressed immediately when it occurs, it may cause further engine problems. If the camshaft position sensor malfunctions, the car may stall while driving.


Error P0340 is used to inform the car owner that their car has problems with the camshaft position sensors. The sensors are installed to tell the PCM the rotational speed of the camshaft. This information is used by the PCM to determine the fuel injection and ignition timing.

The wrong timing leads to misfiring and fuel inefficiency. If you have a defective sensor, you must expect the fuel injector and ignition spark to be switched off. The check engine light often accompanies error P0340. To correct the problem, make sure that the camshaft position sensors are working and receiving the correct voltage. You can clean dirty sensors while replacing worn wires. It is important that you correct error P0340 at the moment it occurs, as it will cause further engine problems if you don’t.

1 thought on “ P0340 Camshaft Position Sensor A – Malfunction ”

  1. Great information. I enjoy what you have shared. I am presently working on an Audi A4 Quattro that has a camshafts position sensor error code pop up. I have checked the electrical going to the sensor, and it reads 4.9v as against 5v. Do you think this can cause the problem? Or do I have to check the timing and see if it has skepped a tooth? The car starts easily once it has run for a while, but always takes a long time to start if parked for a long time. Then it also lacks power when driving and stalls on occasion.

  2. Due to very high demand and a high amount of comments, you might have trouble getting your comment answered by me. If you want to get fast answers from a certified automotive technician you should ask your questions here: Ask A Mechanic

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