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Bad Camshaft Position Sensor: Symptoms, Causes, Test, and Fixes

Here's where you can get a thorough understanding of a bad camshaft position sensor
In this article, you’ll learn about bad camshaft position sensor

The following article details an accurate description of the cam/camshaft position sensor. It covers how it works, where to find it and why it’s an essential component in how well your vehicle runs. By the end of the article, you will know how to diagnose symptoms that could indicate a bad camshaft position sensor.

The article will discuss how to repair or change a defective sensor and related components such as the harness wires. The article covers the procedures to follow and any special tools needed to complete the job.

As always, we highly recommend safety first and proper tools for the proper job. Lets’ get started.

What is a Camshaft Position Sensor and What Does a Camshaft Sensor Do?

The camshaft position sensor is an electronic sensor that sends data to the Engine Control Module (ECM) about the exact speed of the camshaft. Sometimes referred to as the CMP, phase detector or cylinder identification sensor, it transmits data necessary for the engine control module to determine ignition timing in addition to fuel injection timing.

Each camshaft will have its own camshaft position sensor. If the vehicle has what is known as DOHC (Dual Overhead Cams), it will have two sensors.

The camshaft sensor ensures the vehicle gets the best fuel economy for the engine. The information provided to the ECM about the speed of the camshaft helps the injection begin.

What is a Camshaft Position Sensor
The camshaft position sensor is an electronic sensor that sends data to the ECM.

The camshaft sensor transmits data to the engine control module about which cylinder is in the power stroke position. The camshaft sensor provides the data necessary for ECM analytics about when ignition and fuel injection must take place in each individual cylinder.

Camshaft Position Sensor Location

The best practice is to look in the engine service manual to locate the camshaft position sensor. In most if not all vehicles, it is located on the engine block itself or the cylinder head. In some vehicles, the CMP might be:

  • Mounted on the front of the cylinder head below the timing belt cover.
  • Mounted on the cylinder head in the rear.
  • On the side of the engine near the oil fill spout.
  • On the left side of the engine.

If you don’t know for sure, refer to the engine service manual. Don’t guess. It can be in locations that are difficult to get to.

Symptoms of a Bad Camshaft Position Sensor

The sensor can become worn down and even fail over time. The problem can be in the circuit, the sensor itself, the connectors or something related to the function of the camshaft sensor. Some of the indications of a faulty camshaft sensor include:

  • The check engine indicator light on the dash lights up. This is a definite sign a problem exists somewhere. The best practice would be to use a scan tool right away to determine why it has come on. The check engine indicator can come on for a variety of reasons.
  • The engine overheats. If the engine cools down and the indicator light comes on again there is a definite problem somewhere.
  • The engine might begin to stall, or the vehicle begins to experience ‘rough idle’. The vibration at engine idle is intensified to the point where the vehicle can shake.
  • A decrease in engine power might mean the CMP is bad and needs to be replaced. If there is a decrease in power from the engine, it might point to a decrease in power of the signal from the CMP to the ECM. The power can sometimes decrease until there is no signal. No power from the camshaft sensor means no power to the ECM. Without power the vehicle will not start at all.
  • The vehicle does get good gas mileage. One thing that might become noticeable is it takes more gas to travel the same distance on a continuous drive or the gas gauge drops faster than in the past through normal everyday driving.
  • Slow acceleration can mean the signal from the camshaft sensor is weak and it’s transmitting a weak signal to the ECM.
  • The car jerks or losses power when you accelerate.
  • Although not too common the car can backfire.
  • Some engines are designed to lock the transmission in a single gear preventing damage to the transmission.
  • Difficulty starting the vehicle. If the sensor is not operating correctly the data it sends to the engine control module will not be synchronized with the actual function of the engine. It will misinterpret the speed of the camshaft.

Keep in mind that these symptoms are not exclusive to a faulty camshaft sensor and might mean there are other issues which need to be addressed.

How to Remove and Replace a Camshaft Position Sensor.

How Serious is the Problem?

Anytime the check engine warning light comes on it’s a serious problem. In the case of a defective or worn camshaft sensor, the problem is serious. This device works in conjunction with other major sensors to ensure your vehicle operates as it was designed to do. If you risk putting off replacing the CMP, there could be irreversible engine damage, up to and including total loss.

What Causes a Camshaft Sensor to Go Bad?

There are different things that can cause the camshaft position sensor to malfunction. It can fail due to use over a long time, moister, water damage and oil build up on the engine. This sensor continuously operates when the engine is on. Whether driving or not if the engine is on, the CMP is working and can get sworn down. In order to monitor camshaft speed, it must be functioning, even when the vehicle is parked. The camshaft rotates if the engine rotates. The parked position only disengages the gears to the transmission. The engine is still turning when the vehicle is parked.

If the vehicle is involved in an accident, it can cause damage to the sensor. If the sensor wires are damaged, the impact can cause the CMP to stop working correctly. Sometimes an oil leak due to a bad head gasket or defective or loose oil cap can cause the signal to the sensor from the wires to be interrupted. In some cases, the camshaft sensor can go bad as a secondary problem related to an issue with another engine component. If the scan tool indicates there is a problem with the camshaft sensor, take care if it right away.

Read more: What Transmission Do I Have

How to Test Camshaft Position Sensor?

Tools Needed

You will need an OBD2 Scan Tool and a digital multimeter


  • Turn the ignition to the on position but do not start the engine.
  • Insert a code sensor tool into the diagnostic port under the dash. The scanner tool is necessary to read the parameters of the camshaft sensor.
  • Press the ‘Read” key on the scan tool. The scan tool may require that you input the make, model and year of the vehicle as well as what test you want to diagnose for. Once you have input the required parameters hit enter and the sensor will display any failure codes.
  • Check to make sure you have a continuity to camshaft sensor from the wires by removing the harness that transmit the signal to the sensor and testing continuity with the multimeter. If there is no continuity, check the harness for frayed or broken wires. Don’t forget to check for moister at the same time
  • If the continuity is good check the sensor itself.
  • Next do an ohms resistance test with the multimeter to assess the correct ohms resistance for the camshaft sensor. You should use the service manual or online data to find the correct ohms for the vehicle. The resistance will be specific for the vehicle make, model and year.
  • If you get an ohms reading within the required range, the sensor is working correctly. A harness conductivity test will indicate if the problem is with the wiring. An ohms resistance test on the sensor itself will indicate if the sensor works correctly.

Bad Camshaft Position Sensor OBD2 Codes

CODE P0340 – will come up which indicates a camshaft sensor malfunction. When this code appears on a scan tool, it indicates the possibility of a bad sensor or other related issues such as the harness wiring.

CODE P0341 – performance problem

CODE P0342 – Low circuit input

CODE P0343 – High circuit input

CODE P0344 – Intermittent input

How To Replace Camshaft Position Sensor

  • Remove the harness wires
  • Remove the camshaft sensor with a 10 mm wrench. Check for chips and damaged cam sprockets.
  • Insert new camshaft sensor
  • Replace harness

How Much Does Camshaft Replacement Cost?

Just to give an idea about why it is important to take you vehicle in for a diagnostic immediately if the check engine light comes on and code P0340 comes up, ponder this.

All these components are associated with the camshaft.

Camshaft Seal$90 - $1,200
Camshaft$200 – UP
Labor$200 – Up Per Hour
ESTIMATE$600 - $2,500

There can be a heavy price to pay if the camshaft sensor is not replaced or the camshaft is damaged. The easiest and most cost-effective way to prevent serious damage to the vehicle is to take it for a diagnostic check immediately when the check engine light comes on.

The camshaft sensor works in synchronization with other sensors. Engine manufacturers install sensors to provide data analytics in order to assess engine performance. Other sensors that are essential and work in unison with the CMP are

Manifold sensorMeasures pressure of manifold
Fuel TemperatureMeasures fuel temperature
Voltage sensorMeasures voltage

These are just a few of the many sensors that work in conjunction with the CMP. If the camshaft senor does not get the correct information to the ECM about the speed of the camshaft and correct timing for ignition, many other things can go wrong.

When your engine does not operate at peak performance, there can be ancillary problems. Simple scheduled maintenance tasks such as oil changes, correct tire pressure, coolant level for climate control and more are all monitored through the ECM.

Your safety and the safety of others starts with making sure your vehicle always runs the way it was designed to do. Driving along at highway speeds and suddenly lose power is not only dangerous, it can cause a serious or fatal accident.

A dash indication for an ‘oil change due soon’ or ‘wiper fluid low’ do not affect the immediate performance the way the check engine light on does. Your vehicle will take care of you if you take care of it. Parts wear out over time and must be replaced.

As mentioned above, the camshaft sensor always operated when the engine is turning. It can wear out over time. The dash indicator is the manufacturers way of telling you it is time to remove and replace a part if necessary.

The camshaft sensor works in conjunction with the crankshaft position sensor to ensure your vehicle continues to operate as it was designed to do.

How To Test Camshaft Position Sensor Demonstrated On BMW.

Read more: Bad Crankshaft Position Sensor: Symptoms, Causes, and Fixes

Tim MillerFounderOBD Advisor

I’m Tim Miller from Denver, Colorado. I’m the founder of obdadvisor.com, an automotive blog about "Auto Diagnostic Tools and Repair Guides". My fan page is facebook.com/autozikcom. I've been working as an automotive mechanic and blogger for over 10 years writing articles to share my experiences and expertise.

Web: https://www.obdadvisor.comEmail: [email protected]
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