How does a Camshaft Position Sensor? | Symptoms of a bad Camshaft Position Sensor

The camshaft and crankshaft are the most important components of the engine. Since the engine uses the readings from both the crankshaft position sensor and the camshaft position sensor, a malfunction of either sensor could affect your engine’s readings and performance. This article mainly explains the bad camshaft position (CMP) sensor working, symptoms, and replacement cost.

What is a Camshaft Position Sensor?

A camshaft position sensor is an electronic device used in an engine to monitor the camshaft position and rotational speed, and sends this information to the powertrain control module (PCM).

The PCM uses this information to control the fuel injection rate in the combustion chamber and ignition timing.

Camshaft Position Sensor

When the air-fuel mixture is ignited at precisely the right time, engine power and fuel economy increase, and exhaust emissions decrease.

Functions of Camshaft Position (CAM) Sensor

The followings are the common functions of a camshaft position sensor:

  • To determine which cylinder is on its power stroke, a camshaft position (CMP) sensor is used by the car’s computer to monitor the rotating position of the camshaft relative to the crankshaft position. This information will be used to alter the spark timing and fuel injector operation.
  • The CAM sensor is responsible for informing the PCM of the camshaft position. The crank and cam sensors are in time with one another. In a sequential system, the CAM sensor is typically employed to determine which injector to fire and for the COP or coil-on-plug ignition system coil firing event.

The CAM sensor collects and communicates data on the vehicle’s camshaft speed to the powertrain control module (PCM). The PCM uses this information to determine the ignition timing as well as the timing of the fuel injection required by the engine. The engine would not be able to work effectively without this information.

Bad Camshaft Position Sensor Symptoms

As the camshaft position sensor goes bad, it produces one of the below-given symptoms:

  1. Engine won’t start
  2. Check engine light illumination
  3. Car jerking
  4. Ignition issues
  5. Poor engine performance
  6. Fuel system issues
  7. Engine misfire
  8. Engine stalling
  9. Poor acceleration
  10. Transmission issues
  11. Rough idling
  12. Failed emissions test
  13. Gas smell
  14. Poor fuel economy

1) Engine Won’t Start

The most common sign of bad camshaft position sensor symptoms is that the car will be more difficult to start or not start at all.

Engine Won’t Start, symptoms of bad camshaft position sensor

As the camshaft sensor becomes weaker, it does not send the signal to the onboard computer, so the ignition system cannot produce a spark correctly.

No spark means that the engine will not start at all, indicating that the camshaft sensor has failed. Newer cars will detect that the camshaft position sensor is not functioning properly, then they will use the crankshaft position sensor instead.

2) Check Engine Light Illumination

The check engine light illumination is one of the most common symptoms of a bad camshaft position sensor. The check engine light illuminates for many reasons.

check engine light

In a lot of cases, the only symptom you will have from a bad camshaft position sensor is a check engine light on your dashboard.

If the check engine light on your car lights up, it is recommended that you visit a car specialist and have your car scanned to check the trouble codes. You can also do this with an OBD scanner at home. People usually ignore the check engine light without knowing that this could be a sign of something serious, including engine damage.

Read More: Causes of Check Engine Light Illumination  

3) Car Jerking

If you are driving your vehicle and the camshaft position sensor starts failing, the engine will sometimes simply lose power and cause your car to jerk or randomly surge forward.

vehicle Jerking

This happens due to the wrong amount of fuel injected or the engine losing power while the vehicle is in motion. The jerking motion is the car’s reaction to any of these situations.

4) Ignition Issues

As a camshaft position sensor starts having problems and weakens, the transmitted signal to the car’s computer weakens as well. This means the signal is so weak that it will not allow the car to start since there will be no spark from the ignition.

5) Poor Engine Performance

One of the most common problems due to a poor camshaft position sensor is the engine’s power drops dramatically. You will notice frequent stalling, idling, and engine speed drops. Fuel efficiency will also decrease.

poor engine performance

All these problems should be addressed immediately, and they usually occur because of a damaged camshaft position sensor. This is most often because the engine can go into Limp mode when you have a broken camshaft sensor.

6) Fuel System Issues

The CMP sensor controls the amount of fuel that goes into the car’s engine cylinders. It does this by sending signals to the car’s computer that allows it to fix the timing and duration of the fuel injected into the engine’s cylinders.

fuel injection system working

A bad CMP sensor can no longer perform this task as there is no longer any pulse on your car’s fuel injectors. This situation affects the function of the fuel system and leads to other issues.

Read More: Fuel System Working and Parts

7) Engine Misfire

The engine misfiring is one of the most common causes of a bad camshaft position sensor. If you feel that your car engine’s performance got reduced, together with a check engine light on the dashboard, it’s definitely time to check your car’s trouble codes.

Engine Misfiring

8) Engine Stalling

Your car may experience stalling issues when the CMP sensor goes bad. This is because when your car’s CMP sensor goes bad, the fuel injectors no longer receive signals to send fuel to the engine cylinders at the appropriate times. Once that happens, the engine loses power, and it starts stalling.

At this stage, the engine can go into limp mode. This is a situation where the car locks into a single gear and does not accelerate beyond a certain speed.

engine Stalling due to bad camshaft position sensor

Read More: Causes and Symptoms of Limp Mode

9) Poor Acceleration

The fuel delivery issues caused by a bad CMP sensor will eventually affect how the vehicle accelerates. The reason is that the signals sent from the failing CMP sensors are either wrong or irregular. This affects the ignition timing and amount of fuel injected, which affects the way the throttle responds and ultimately leads to poor acceleration.

acceleration problems

10) Transmission Issues

Some cars with automatic transmissions won’t change gears properly if you have a bad camshaft position sensor.

Drivers of automatic transmissions with a bad CMP sensor will find that the transmission is locked and that the vehicle does not go beyond a single gear. This also occurs when the car has entered the limp mode.

11) Rough Idling

Rough idling of the engine can also be caused by a failure of the camshaft position sensor. When the camshaft sensor goes bad, rough idle occurs due to asynchronous combustion in the cylinder.

Rough Idling

It could also be the result of a bad idle fuel pump or EGR (exhaust gas recirculation) valve. Whatever the reason, it’s important to know what causes rough idling, and it may require some additional tools and testing to figure it out.

Read More: Why My Car Shuts Off While Driving

12) Failed Emissions Test

When the engine is not performing properly, it will not be able to burn fuel efficiently. This can lead to increased emissions.

Failed Emissions Test

13) Fuel Smell

A faulty camshaft sensor can indirectly dump unburned fuel into a vehicle’s exhaust system. This affects the fuel economy and can cause some irritating black smoke from the tailpipe. This unburned fuel gas from the tailpipe causes a noticeable smell which is very dangerous for people.

smell of unburnt fuel

14) Poor Fuel Economy

Lowered power because of the camshaft position sensor can also cause a higher fuel consumption. This is pretty rare when it comes to a faulty camshaft position sensor, but it is not impossible.

Poor fuel economy

If you experience a high fuel consumption, you should absolutely check the trouble codes for any codes related to the camshaft position sensor.

Read More: Bad Crankshaft Position Sensor Symptoms and Causes

Causes of a bad Camshaft Position Sensor

The following are the major causes of a camshaft position sensor going bad:

  1. Insufficient maintenance of the vehicle
  2. Grime and oil in the engine
  3. Wear and tear
  4. Age of the sensor
  5. Water damage
  6. bad wiring
  7. Engine overheating

Camshaft Position Sensor Location

The Camshaft Position sensor is typically located in the cylinder head of the engine and has a cylindrical portion that inserts into the head.

Camshaft Position Sensor Location

The crankshaft position sensor is normally located in the timing cover or on the side of the block with a cylindrical portion that inserts into the block.

How to replace a Camshaft Position Sensor?

Follow the below-given steps to replace a cam sensor:

  1. First of all, disconnect the negative battery cable.
  2. Locate the sensor. It’s usually on the top, front, or rear part of the engine. It will likely have a 2-3 wire connector attached.
  3. Release the tab on the sensor to disconnect the wires from the sensor.
  4. Remove the mounting bolt which attaches the sensor to the engine. It’s usually an 8mm or 10mm bolt.
  5. Pull the sensor off with a slight twist.
  6. Apply a bit of engine oil to the O-ring of the new sensor.
  7. Install the new camshaft position sensor and secure it with the mounting bolt.
  8. Reconnect the wire connector to the sensor.
  9. Reconnect the negative battery terminal and start your engine.

Camshaft Position Sensor Replacement Cost

The replacement or repair cost of the camshaft position (CMP) sensor varies according to vehicle model, labor cost, and the type of part brand.

The average replacement cost of the camshaft position sensor is from $90 to $260. The labor cost is from $25 to $120, while the part itself costs from $75 to $140.

A CMP sensor replacement cost in a luxury car may be higher. If you don’t replace the sensor yourself, the labor cost of replacement may be $25 to $120

Labor Cost$25 to $120
Part Cost$75 to $140
Camshaft Position Sensor Replacement Cost$90 to $260

FAQ Section

What does a bad camshaft sound like?

Bad camshaft often makes certain sounds that let you know that something is wrong with it. Most times, a bad camshaft often comes with ticking, tapping, and popping sounds. You will also hear lots of backfiring as the car engine’s cylinders frequently misfire at different speeds.

What is the function of the camshaft position sensor?

The camshaft sensor’s core functionality is to work in combination with the crankshaft sensor of your vehicle. The main function of the camshaft position sensor is to determine the position of the camshaft drive very precisely. As a result, it generates signals in the same way as the crankshaft position sensor. It helps the powertrain control module (PCM) to determine the exact time the first cylinder is in the top dead center position.

The PCM uses the information generated by the camshaft for various purposes. Essentially, the information helps to start the injection process during the sequential injection. It also supports the actuation signal for the pump nozzle injection system and calibrates the knock control.

The Hall principle is the core working concept of a camshaft sensor. 

Can I drive with a bad camshaft position sensor?

It’s not recommended to drive with a bad camshaft position sensor, even if you most likely can.

If your camshaft position sensor is bad, it will likely cause your car to run poorly and may even cause it to not start. However, it will most likely not cause your car to shut off, but I wouldn’t recommend doing that anyways. It’s best to have the sensor replaced as soon as possible.

How to reset the camshaft position sensor?

Unfortunately, there’s no way to reset a camshaft position sensor. You’ll have to replace the part if you’re having camshaft issues (sputtering, acceleration trouble, check engine light illumination and stalling, etc.).

Is it safe to drive with a bad camshaft sensor?

Yes, it is safe to drive with a bad camshaft sensor. However, the performance of your engine will not be as good, and fuel consumption may increase. If you have any trouble with your camshaft sensor, there are a few ways to test and diagnose the problem.

How to clean a camshaft position sensor?

  • Disconnect the negative battery cable
  • Locate the camshaft sensor
  • Remove the three wires from the sensor; remember where they go so you can install them back properly.
  • Remove the camshaft sensor and place it on a clean towel
  • Spray a small amount of solvent on the sensor, and wipe it dry
  • Replace the camshaft sensor, re-install the three wires in their original spots, and reconnect the negative battery cable

How long does a camshaft sensor last?

The cam sensor is built to last the life of the car, and there is no set maintenance schedule for when the camshaft position sensor should be replaced. It only needs to be replaced when it is damaged or bad.

What is the difference between the camshaft position sensor and the crankshaft position sensor?

The main difference between camshaft and crankshaft position sensors is that the camshaft position sensor is used to find the position of the camshaft while the crankshaft position sensor is used to detect the position of the crankshaft and piston.

What happens when a camshaft sensor goes bad?

As the camshaft sensor goes bad, it gives one of the below-given symptoms:

  1. Engine won’t start
  2. Poor fuel economy
  3. Check engine light illumination
  4. Rough idling
  5. Car jerking
  6. Ignition issues
  7. Gas smell
  8. Poor engine performance
  9. Fuel system issues
  10. Engine misfire
  11. Failed emissions test
  12. Transmission issues
  13. Engine stalling
  14. Poor acceleration

How many camshaft sensors does a vehicle have?

Generally, a new car should have four camshaft sensors, one for each camshaft. A camshaft sensor determines the exact position of your engine’s camshaft, helping your car keep your engine’s combustion running smoothly.

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