Troubleshoot Engine

How to Know If Your Camshaft Sensor is Failing: 7 Symptoms to Watch For

symptoms of a bad camshaft position sensor

The camshaft sensor plays a major role in keeping the timing of your engine on track. It monitors the position of the camshaft and crankshaft to determine the position of the pistons. If the camshaft sensor is not working properly then it will severely impact engine performance.

The symptoms of a bad camshaft position sensor can include poor engine performance, lack of power when accelerating, a rough engine when idling and when pulling away, poor fuel economy, engine error codes and a check engine light on the dashboard.

The camshaft sensor monitors the position of the camshaft by scanning the ring gear on the spinning camshaft. Some engines have more than one camshaft sensor, so it’s necessary to use an OBD scanner when trying to diagnose problems with the sensor.

In this article, we’ll look at the most common symptoms you may notice if a camshaft sensor is failing and how you can go about diagnosing and repairing it.

What happens when a camshaft sensor goes bad? (7 Symptoms With Fixes)

A bad camshaft sensor can cause a variety of issues with your car’s engine. Common symptoms of a bad camshaft sensor include poor engine performance, rough idling or stalling, reduced acceleration, and poor fuel economy. Usually, a failing camshaft sensor will also trigger the check engine light to come on and cause the engine to misfire.

If the ECU can’t accurately keep track of the camshaft position as it rotates, then this is going to affect the timing of the pistons and valves.

Many engines use variable valve timing, where the camshaft sensor is needed to differentiate the compression from the exhaust stroke. If the sensor is not working properly, there is a good chance that the spark plug will be firing twice per stroke. This means that the engine will probably keep running, but as well as it should.

It’s possible that the symptoms of a bad camshaft sensor can be confused with issues with the timing belt or timing chain. 

The best way to diagnose a faulty camshaft sensor is to run a diagnostic to check for engine error codes. Error code P0340 means that there is something wrong with the camshaft position sensor or the camshaft sensor circuit.

Here are the most common symptoms of a bad camshaft position sensor:

1. Check Engine Light on the dashboard

A broken camshaft position sensor is going to impact the timing of the engine, especially the fuel delivery timing. If the ECU stops receiving a signal from the camshaft sensor, then this indicates a problem with the sensor or some other part of the camshaft sensor circuit.

check engine light flashing

This will cause the check engine light to flash or stay on. If the sensor is still sending a signal to the ECU, then chances are the check engine light won’t come on, and it may indicate a problem with another part of the engine such as the ignition coils or spark plugs.

2. Poor Fuel Economy

A bad camshaft sensor can impact fuel efficiency in a few ways. The camshaft sensor is responsible for monitoring the position of the camshaft and sending this information to the engine control unit (ECU). The ECU uses this information to determine the optimal fuel injection and ignition timing for the engine.

If the camshaft sensor is faulty or failing, it can send incorrect signals to the ECU, causing it to adjust the fuel injection and ignition timing improperly. This can result in the engine running rich, which can cause a decrease in fuel efficiency.

A bad camshaft sensor can cause the engine to misfire or hesitate during acceleration, which can result in increased fuel consumption.

The engine may also run rough or stall, which can cause the fuel system to become flooded and lead to even worse fuel economy.

3. Rough engine Idle with Vibrations

A very common symptom of a failed camshaft position sensor, is a rough or vibrating engine.

This will be more noticeable when stopped and the engine is idling. If there is no wind or road noise, the movement and noise from the valves and pistons is more noticeable, especially if the timing is slightly out.

It’s also possible that a rough engine idle can also be caused by a stuck or failing idle air control valve.

4. Engine Hesitation During Acceleration

A delay in acceleration and a lack of engine power is common with a bad camshaft sensor.

The job of the camshaft position sensor is to tell the ECU where in the cycle the engine currently is.  

The ECU uses this information to control the timing of the firing of spark plugs and the injection of fuel.

Any problems with the timing will cause a hesitation when you press the accelerator and will usually be accompanied by lurching and stalling of the engine.

5. Engine Stall 

If the ECU can’t keep track of the timing sequence of the engine, then this can cause the engine to cut out.

In this case, a stalled engine can be caused by a lack of fuel but more often than not, it’s actually an intentional shut down to protect the engine from damage.

If the ECU detects a problem with the camshaft sensor circuitry, then it may cut out the engine, or stop it from starting.

6. Increased Emissions 

A bad camshaft position sensor can cause increased emissions as a result of engine misfiring.

The camshaft position sensor helps regulate the engine’s timing, which affects the amount of fuel that enters the combustion chambers and the exhaust emissions produced by the engine.

If the sensor is faulty and provides inaccurate feedback to the ECU, the engine may misfire, leading to incomplete combustion and increased emissions.

7. Gas Smell From Exhaust Pipe 

A failure to deliver the exact amount of fuel to the engine, may result in unburnt fuel making its way into the exhaust gases and out through the tailpipe. This can cause a noticeable gas smell, especially when idling.

What is a Camshaft Position Sensor And How Does It Work?

The Camshaft Position Sensor (also known as the CMP sensor) is one of the key sensors when it comes to the smooth running of your engine. 

camshaft position sensor
A typical camshaft position sensor

The information it generates plays a crucial role in determining when each injector should be activated on a modern sequential fuel injection systems (SFI).

The camshaft position sensor is responsible for sending the ECU a signal each time the cylinder #1 intake valve is opening.

That information is then used in conjunction with the Crankshaft Position Sensor (CKP) signal for knowing when the rest of the cylinders’ intake valves are opening.

Camshaft Position Sensors use the same electronic principles of other engine sensors such as Crankshaft Position Sensors.

In other words, they are so similar in construction they are often difficult to differentiate from one another when outside the vehicle.

There are two common types of sensors. The design can be based on “optical”, “inductive”, or “Hall Effect” principles. For the purpose of this article, we will explain the Hall Effect design.

Hall Effect sensors consist of two key elements, the reluctor ring (toothed wheel) and the sensor itself which internally has a permanent magnet.

camshaft position sensor

The reluctor is attached to the camshaft in a way that cylinder #1 intake valve opening coincides with the “tooth”.

Many designs include all cylinders (not only cylinder #1) but using a wider tooth for differentiating #1 which will always be the “reference”.

As the camshaft rotates the permanent magnet inside the sensor will induce an electrical current each time the tooth aligns with it. The Hall sensor signal produced this way is similar to a square waveform like the green like shown below: 

symptoms of bad camshaft sensor

The ECU uses this information for the fuel injectors “firing” sequence, thus the importance of an accurate reading.

How Do You Diagnose A Bad Camshaft Position Sensor?

Diagnosing a bad camshaft position sensor is not a difficult process, especially if the check engine light.

A check engine light is usually accompanied by diagnostic trouble codes that can be retrieved using a diagnostic readout of the ECU. I’d recommend start by using an OBD-II scanner to see if the cause of the problem is the camshaft sensor, and to identify which sensor is at fault if there is more than one fitted.

I’d also recommend getting your hands on a service manual for you exact vehicle. This will outline the exact steps involved in identifying and replacing the camshaft sensor if necessary

Here is a general outline of the process of diagnosing a faulty camshaft sensor:

  1. Consult the Vehicle’s Service Manual: Start by referring to the service manual specific to your vehicle. It will provide information on the location of the camshaft position sensor and any specific diagnostic procedures recommended by the manufacturer.
  2. Visual Inspection: Perform a visual inspection of the sensor and its wiring harness. Look for any signs of physical damage, loose connections, or corrosion. Ensure that the sensor is securely mounted and that there are no obstructions or debris blocking its operation.
  3. Check for Error Codes: Use an OBD-II scanner to retrieve any stored diagnostic trouble codes (DTCs) related to the camshaft position sensor. These codes can provide valuable clues about the nature of the problem. Common codes related to the camshaft position sensor include P0340, P0341, P0345, and P0346.
  4. Test the Sensor’s Voltage: With the engine off, use a multimeter to check the voltage output of the camshaft position sensor. Consult the service manual for the specific voltage range that the sensor should produce. If the sensor is not within the specified range, it may indicate a faulty sensor.
  5. Inspect the Sensor’s Signal: Some camshaft position sensors generate an AC voltage signal, while others produce a digital signal. Use an oscilloscope or a digital multimeter to measure the signal waveform produced by the sensor. Compare it to the specifications provided in the service manual. Any irregularities or inconsistencies in the signal may indicate a faulty sensor.
  6. Test the Wiring and Connections: Inspect the wiring harness and connectors associated with the camshaft position sensor. Ensure that the connections are clean, secure, and free from corrosion. Use a wiring diagram to check for continuity and proper voltage supply along the sensor’s circuit.
  7. Perform a Functional Test: If the previous steps do not conclusively indicate a faulty sensor, you can perform a functional test. This involves using a diagnostic scan tool capable of monitoring real-time sensor data. Start the engine and observe the camshaft position sensor’s readings to ensure they are within the expected range during engine operation.

The exact diagnostic process may vary depending on the vehicle make and model. If you don’t know what you re doing seek the assistance of a qualified mechanic who has experience with your specific vehicle. They will have the necessary tools and expertise to accurately diagnose and address any issues with the camshaft position sensor.

How much does it cost to replace a bad camshaft position sensor?

The cost of replacing a bad camshaft position sensor can vary depending on several factors, including the make and model of your vehicle, the location of the sensor, and labor costs in your area.

On average, the cost of a camshaft position sensor replacement ranges from $100 to $250.

Keep in mind that this estimate is for the sensor itself and does not include any additional costs that may arise during the replacement process. If you choose to have the sensor replaced by a professional mechanic, there may be additional labor charges.

What Are The Effects of A Faulty Camshaft Sensor On Ignition Timing?

A faulty camshaft sensor can have significant effects on ignition timing, which can have a negative impact on engine performance.

Here are some effects that can occur when the camshaft sensor is not functioning properly:

  1. Erratic Ignition Timing: The camshaft sensor plays a key role in synchronizing the opening and closing of the engine’s intake and exhaust valves with the ignition system. When the sensor is faulty, it may not provide accurate timing information to the engine control unit (ECU). As a result, the ignition timing can become erratic, leading to misfires, rough idling, or poor acceleration.
  2. Reduced Power and Performance: Inaccurate ignition timing caused by a faulty camshaft sensor can result in reduced power and performance. The engine may struggle to generate the necessary power during acceleration or under heavy load. This can lead to sluggishness, a decrease in overall engine performance, and a noticeable loss of power.
  3. Poor Fuel Efficiency: Ignition timing plays a crucial role in optimizing fuel combustion within the engine cylinders. When the camshaft sensor provides incorrect timing information, it can disrupt the precise synchronization of fuel delivery and ignition. This can lead to incomplete combustion, wastage of fuel, and decreased fuel efficiency.
  4. Increased Emissions: A malfunctioning camshaft sensor can cause improper ignition timing, leading to incomplete combustion. Incomplete combustion can result in unburned fuel being released into the exhaust system, leading to increased emissions of pollutants such as hydrocarbons (HC) and carbon monoxide (CO).
  5. Engine Stalling or Failure to Start: In some cases, a faulty camshaft sensor can cause intermittent or complete engine stalling or even prevent the engine from starting altogether. If the sensor fails to provide the necessary timing information, the ECU may struggle to operate the ignition system properly, resulting in engine misfires or failure to ignite the fuel-air mixture.

How Do You Reset A Camshaft Position Sensor?

The process for resetting a camshaft position sensor can vary depending on the vehicle make and model. However, here are general steps that may apply:

  1. Disconnect the battery: Disconnect the negative terminal cable from the battery and ensure it is properly tightened.
  2. Locate the sensor: Use your owner’s manual or online resources to locate the camshaft position sensor, which is a small tube- or disc-shaped part with bolt and wire connections.
  3. Remove the sensor: Disconnect the sensor electrical connector and remove the sensor from its mounting.
  4. Clean the sensor: Clean the sensor using a soft cloth or a cleaning spray.
  5. Reinstall the sensor: Reinstall the sensor and ensure it is properly secured.
  6. Reconnect the battery: Reconnect the negative terminal cable to the battery and ensure it is properly tightened.
  7. Turn on the ignition: Start the vehicle’s engine and observe if the camshaft position sensor functions correctly. Monitor for any warning lights or abnormal engine behavior.

Some vehicles may require a diagnostic scanner to reset the camshaft position sensor, and it may be best to consult a professional mechanic for assistance.


1. What does a car sound like with bad camshaft sensor?

A car with a bad camshaft sensor can produce a variety of unusual sounds, depending on the severity of the problem. These sounds can include engine misfires, rough idling or stalling, hesitation or stumbling during acceleration, and whining or ticking noises. These noises may be due to improper fuel injection or ignition timing caused by the faulty sensor.

2. Is it ok to drive with a bad camshaft position sensor?

 It is generally safe to drive with a bad camshaft position sensor for a short period of time. However, the engine’s performance may be affected, and fuel consumption may increase. It is important to note that driving with a bad camshaft position sensor can also cause other issues such as engine misfires, stalling, and difficulty starting the engine. Therefore, it is recommended to have the sensor replaced as soon as possible to avoid further damage to the engine and potential safety hazards while driving.

3. Is crankshaft position sensor the same as camshaft position sensor?

No, the crankshaft position sensor and the camshaft position sensor are not the same. While they are both sensors that detect the position of engine components, they serve different purposes.
The crankshaft position sensor detects the position and rotational speed of the crankshaft, which is connected to the pistons and is responsible for the engine’s power output. The sensor provides this information to the engine control module, which uses it to control the fuel injection and ignition timing.
On the other hand, the camshaft position sensor detects the position and rotational speed of the camshaft, which controls the opening and closing of the engine’s valves. The sensor provides this information to the engine control module, which uses it to determine the correct timing for fuel injection and ignition.

4. Can a camshaft sensor be cleaned?

Yes, a camshaft position sensor can be cleaned. If the sensor is dirty or covered in oil, it may not function properly, leading to engine performance issues. Cleaning the sensor can help restore its function.
To clean the camshaft position sensor, you can use a cleaning solution such as a carburetor cleaner or an electrical contact cleaner, along with a microfiber cloth to wipe away any debris or buildup. It is important to be gentle when cleaning the sensor and not to use any abrasive materials that could damage it.

5. How long does a camshaft position sensor last?

The lifespan of a camshaft position sensor can vary depending on the vehicle make and model, as well as the driving conditions and maintenance of the vehicle. However, camshaft position sensors are generally designed to last the life of the vehicle.
That being said, camshaft position sensors can fail prematurely due to factors such as exposure to high temperatures, oil contamination, or electrical issues.

About the author

The Motor Guy

The Motor Guy is a passionate car enthusiast with a love for troubleshooting and diagnosing all sorts of vehicle problems.

With years of experience in OBD diagnostics, he has become an expert in identifying and solving complex automotive issues.

Through, he shares his knowledge and expertise with others, providing valuable insights and tips on how to keep your vehicle running smoothly.

- 12 years experience in the automotive industry
- ASE Master Automobile Technician
- A Series: Automobile and Light Truck Certification, A9 Light Vehicle Diesel Engine Certification
- Bachelor's Degree in Information Systems