Ask Car Mechanic

Ask Car Mechanic

How To Fix It

Bad Camshaft Position Sensor Symptoms


Bad Camshaft Position Sensor Symptoms

People don’t realize how many sensors are in their cars or how important they are to driving. There used to be parts like carburetors and distributors but modern cars have sensors. It has lots of sensors. One of those is a camshaft position sensor. 

There are symptoms to let you know something is going on that needs to be checked. Bad camshaft position symptoms include bad fuel economy, trouble accelerating, a check engine light, and stalling. These could signal other problems too, so it’s good to get it checked. 

What Does the Camshaft Position Sensor Do?

The camshaft position sensor tells the computer when to ignite and send fuel. It projects the exact time the first cylinder is in the right position to fire, which is the top dead center position.

It is kind of like your eyes feeling the morning sun and telling the brain to wake the body up. The sensor goes into action when you try to start the car. Most people don’t even know it is reacting because it all happens so quickly and effortlessly until the sensor starts going bad. 

Read: Is Driving With a Bad Oil Pressure Sensor a Good Idea?

Where Is the Camshaft Position Sensor Located?

The sensor will always be on the camshaft but it can be either on the top of the valve cover or on the side of the cylinder head.

What Makes a Sensor Go Bad?

Most car sensors, including the camshaft position sensor, wear over time. Sensors like this one are always working while the car is running. The ring gear can become worn or it can be damaged with cracks or by an oil leak.

What Are the Signs of a Bad Camshaft Position Sensor?

Six signs of a bad camshaft position sensor will become noticeable to most vehicle owners, even if they don’t know much about cars or their vehicles. 

1. Car Won’t Start

This is the first clue that the camshaft sensor may be bad. It is an important clue as some may fault the ignition switch and seek to replace it before looking at the camshaft sensor. That is a waste of money. 

It could be that your car starts but is having trouble. It has more trouble as time goes on. That is because the engine is missing an important component of combustion: spark. 

A weakened camshaft sensor means it can’t send a proper signal to the car’s computer and so the ignition system can’t produce a good start. The sensor grows weaker over time so your vehicle will be harder to start.

2. Check Engine Light Appears

Yes, this is aggravating. In truth, the check engine light could mean many things. However, the car’s computer system stores error codes so a scanner can determine which codes are being generated to turn on the check engine light. 

A scanner can determine the codes that are causing the check engine light to show up. The diagnostic trouble code (DTC) for the camshaft position sensor is P0340. 

While this refers to the camshaft position sensor, the code is a general one and there could be any number of problems associated with the sensor. You will likely need a mechanic to diagnose further to identify your exact problem.

For some vehicle models, the check engine light may be the first symptom of a camshaft sensor issue. It could be the only symptom too but that doesn’t mean the problem is less severe than if you have multiple issues. It’s still the same problem and it will get worse over time.

A bad sensor can lead to significant engine and transmission issues so you don’t want to let it go just because you only are seeing the one symptom of a check engine light.

Read: What Does The Service Engine Soon Light In My Car Mean?

3. Poor Performance

This is one of those symptoms that could be several things but poor engine performance is a sign of a bad camshaft sensor. It could be that your car is sluggish to move or stalls. You may have a sudden drop in speed or rough idling. All of these could mean a faulty sensor. 

Poor performance can be a risky situation too because you never want your vehicle to start acting on its own, like suddenly dropping in speed or stalling. That can cause an accident or leave you stranded on the side of the road waiting on a tow truck.

4. Misfires and Vibration

Your car feels like it is backfiring or is missing a beat in acceleration. This gives the vehicle a bit of vibration when it accelerates. It is likely due to a camshaft position sensor going bad. 

Misfiring and vibrations are some of the more dangerous symptoms because it could cause some real issues if it happens while in traffic. Plus, it becomes a real hassle when trying to accelerate or merge. 

5. Issues with Shifting Gears

Most people think of transmission problems when it comes to trouble with moving from gear to gear. However, this is also a signal of other problems which can include the camshaft position sensor. 

This is a common symptom in automatic cars. Automatic cars have a “limp mode” that they will move into if there are problems with the engine. Limp mode prevents the car from high performance and keeps it slow-moving to protect the car from damage. This may be the reason why your vehicle won’t’ go into a higher gear. 

Look in your owner’s manual to see if your vehicle has a limp mode feature and how to identify if it’s running in that safety feature.

6. Bad Fuel Economy

This is a rare symptom of a camshaft position sensor issue but it remains one of the possible issues your vehicle can experience. Those noticing that the vehicle isn’t getting the same fuel savings it used to should take it in to get it checked out. It could be this sensor, a TPS sensor, or some other problem. 

The money you spend on a quick diagnostic will be saved in future fuel savings once you get the issue fixed. 

How Much Does It Cost to Replace?

This is a relatively cheap part to replace. The part will cost between $75 and $120 while the labor can range from $30 to $130, depending on the mechanic’s hourly charge. That makes the average replacement cost between $100 and $250. 

The part prices can vary depending on your car’s make, model, where the part is manufactured and the supplier furnishing it. You can expect the replacement cost to be more in a luxury car. 

Can I Replace the Sensor Myself?

Replacing the camshaft position sensor yourself is a cheaper way to go and can be a good solution if you are comfortable with mechanical work, have the tools and the patience to look at a few tutorials before you try it. 

It doesn’t take any special tools to do this replacement job and you probably already have the tools necessary if you have some screwdrivers and pliers.

There are two ways to get to the camshaft position sensor. The easiest way for most vehicles tends to be from under the vehicle. However, you may also be able to access it from the top of the vehicle by removing the air filter housing. 

After you find the sensor’s location, disconnect the negative battery cable before starting any work.

While you are poking around, check for oil and corrosion in the area. Both can affect the sensor’s attempt to signal the engine’s control module. Cleaning the grime from the sensor and area may resolve the problem without needing to replace the sensor.

Push down the tab on the sensor’s electrical connector and slide it off and then remove the sensors mounting screws using a wrench or a ratchet with a socket. 

Remove the sensor gently. Be sure to check the bottom of it to be sure there isn’t an oil leak problem. 

To install the new sensor, put it straight into place and line up the bolt flange with the mounting hole.

Put in the mounting screws and tighten. Hook up the electrical connector and then reconnect the negative battery cable.


The camshaft position sensor is an inexpensive fix for most vehicles but it can cause major problems if not addressed. Be sure to check the codes and see if the sensor is the root of your car’s problems when symptoms first appear.

Leave a Comment