Camshaft Position Sensor (CMP)

The Camshaft Position Sensor is a precision automotive component. It is used to locate the piston stroke in the cylinder. Its function is parallel to or coincides with the CKP or crankshaft sensor, thus synchronizing spark and injection timing.

What is the camshaft position sensor?


The CMP sensor is an electrical device, with which the ECU receives a position signal, taken from the camshaft. It consists of a coil and a magnetized section. They are available with two or three wires.

How does the CMP sensor work?

At one end of the camshaft is a gear. The sensor, located very close to it, reads each groove or tooth. This voltage signal acts in conjunction with the crankshaft sensor signal. This combined signal allows the engine computer to pinpoint the exact time for each spark plug to spark. In addition to regulating the injection flow for each cylinder at start-up.

This synchronization generates a sequence that initiates the combustion cycle of the engine, and it must be in each spark plug and in each cylinder since the pistons are in odifferent positions in its path. The voltage sent by this sensor is regulated by several factors. Among them, are the speed of rotation or revolutions, the distance from the sensor to the point, and in turn the magnetic field generated by the proximity.

CMP Sensor Types

Camshaft position sensor types are identified based on the type of signal they emit. The other variants you might get in them are by the wiring. You might find sensors with two wires, one positive or power, one signal or voltage, and the grounding is given by the body of the sensor itself. If it is of three wires, one will be the power supply, another signal, and the last terminal will be the ground.

Magnetic sensor

Having a coil creates the magnetic field generating the voltage signal, which travels to the computer. This signal varies according to the speed detected by the sensor.

Hall Sensor

With this Hall Sensor, the signal travels straight in the direction of the magnetic force, when the magnet touches it, the signal will be generated.

Camshaft Position Sensor Failures

A sensor can be of a high, medium, or low criticality in a vehicle's engine. In this case, since it works in conjunction with the crankshaft sensor, and at a certain moment it can supplant its function, we could say that it is of medium criticality.

However, this does not mean that it will not affect performance, since it will allow starting and displacement, but power will decrease. In other cases, depending on the manufacturer, the criticality will become high, because a warning signal is generated for protection and the engine will be shut down.

The most common causes of these failures are due to wiring malfunctions or a problem in the connector, whether it is loose or sulfated.

Interference of the Camshaft Position Sensor on other systems

The function of this sensor is indispensable in fuel injection engines. Thanks to this, it is possible to control the spark ignition moment and the precise instant of the opening of the fuel injectors for each cylinder. After starting, the cycle is maintained, achieving the expected performance.

Within the ODBII protocol, some generic fault codes of this sensor can be diagnosed, and they are the following:

P0334: This means that the signal is not stable or missing. Usually, it is a fault concerning the electrical circuit.

P0341: Indicates that a fault occurred in the injection sequence.

P0342: Its meaning indicates a lack of starting power. A problem that can result from low battery amperage, or failure of the vehicle's starter motor.

Symptoms of a damaged Camshaft Position Sensor

When your vehicle's ECU detects a sensor failure, it will immediately display a signal on your Check Engine panel. Other symptoms that the CMP function is not optimal include the following

  • Hard, erratic starting with jerking.
  • ECU with "emergency mode activated" signal.
  • The engine shuts down and does not restart.

How to test the CMP Sensor?

To check the condition of the CMP Sensor you must have a multimeter and a magnet. This way you will be able to perform a fairly simple and easy test:

  • After removing the sensor, bring the magnet close to it and you should see that the reading on the multimeter varies from 0 to 12 volts. If there is no voltage signal or variations it means that it is damaged.
  • Now you can identify the wiring to the ECU, guided by the branches of the vehicle or by following the electrical diagram.
  • Then, with the multimeter, measure the continuity, trying to rule out that the circuit is open.

How to clean the Camshaft Position Sensor?

Actually, it does not require cleaning as such. The connector can become sulfated and you can clean it with an electronic cleaning spray. If the wiring is damaged, you can repair it. Although it is best for the sensors that their wiring is free of splices and soldering.

CMP Sensor Location

The Camshaft Position Sensor is mostly only present or integrated into fuel injection ignition vehicles, i.e. those that do not have a distributor. Specifically, it is located in the cylinder head or cam, to which the camshaft is attached. So, the location is in the head of your engine. You can find out the exact location of the CMP sensor by acquiring the car's electrical diagrams.


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