Error Code P0343 is defined as Camshaft Position Sensor “A” Circuit High Input. Meaning, the problem refers to the camshaft position sensor, which has been fouled from the combination of oil and moisture, causing bad ground or voltage.

This code is a generic trouble code, meaning it applies to all vehicles made since 2003. It is more common among particular makes, such as Chevrolet, Ford, Hyundai, Kia, Toyota, and VW vehicles. Some vehicles makes however, can still have this code. Specifications on the definition, troubleshooting and repairs vary from one make and/or model to another.


Error Code P0343 refers to a voltage problem with the CMP or camshaft position sensor. This sensor is a fixed electromagnetic sensor connected to the rotating part of the camshaft, which works by recording the position of the “teeth” to indicate the stroke of the pistons, giving the computer of the vehicle or PCM (powertrain control module, also called as ECM or engine control module in other makes) the information to appropriate the right fuel and spark for the engine.

The position of the camshaft makes various gaps between the sensor, and this change in magnetic field changes the voltage from the sensor.

Error Code P0343 is set when the voltage detected is not within the parameters set by the manufacturer, and it applies to the Bank 1 sensor that monitors the cylinder # 1.

Common Symptoms

A defective CMP sensor can cause the PCM to provide incorrect amount of fuel and spark, leading to various drivability conditions, such as inconsistent starting issues and stalling. Other common symptoms for Error Code P0343 are:

  • Bucking or surging
  • For inconsistent problems, the engine may die out then restart
  • Vehicle may run fine until it cuts out, then will not restart again

Possible Causes

There are many reasons for a vehicle to register this code. Some of the most common possible causes include:

  • Open in ground circuit to the CMP sensor
  • Short to 5V in the signal circuit to the CMP sensor
  • Open in the signal circuit between the CMP sensor and the PCM
  • Internally shorted to voltage CMP

Other causes include:

  • Defective CMP sensor
  • Defective power wiring
  • Defective ground wiring
  • Defective starter motor
  • Weak or dead battery
  • Faulty PCM (rare)

How to Check

Mechanics start their diagnosis for their error code through a thorough visual inspection of the sensor and determine whether or not it is being fouled due to an oil leak, damaged or frayed wiring.

Note that, sensors can be cleaned to work back to normal. Technicians usually use electrical contact cleaner or even rubbing alcohol to clean these components and clear the codes.

If the code comes back, then there’s a good chance that the problem is in the sensor itself. To be sure about this, you can use a multimeter and a test light to test whether the sensor is getting the voltage supply it needs to function properly. If it does not get the voltage it needs, then the mechanics will replace the sensor with a high-quality replacement part. The codes are then cleared and the vehicle will be taken to a test drive to ensure the new sensor works properly and the code doesn’t come back.

How to Fix

Some of the most common fixes for this code include:

  • Replacement of the CMP sensor
  • Replacing damaged connectors or wirings
  • Repairing of nearby oil leaks
  • Cleaning the ground wires

CMP sensors are crucial for modern vehicle’s fuel injection. Error Code P0343 must be addressed quickly, as it affects the driving quality of the vehicle

Also, this error usually involves bad replacement sensors. It is imperative that one should use high quality replacements to avoid the hassles and inconvenience of the problem.