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Camshaft Position Sensor Symptoms & Replacement Cost


Modern engines are increasingly equipped with computers and sensors to control every moment of the operation of the engine. These computers and sensors manage fuel injection, engine performance and improve the emission controls mandated by various governments.

The primary computer system managing the engine performance is the Engine Control Unit or ECU. Gasoline engines must manage the mixture of fuel, air, and the spark that ignites the mixture.

The combination of sensors feeding data into the ECU allows the ECU to ensure that maximum power is provided to the transmission when needed, burn as little fuel as possible and produce as little pollution as possible.

If the timing of the spark is off or if the mixture is off, the engine may not run at all or run rough, producing little power and potentially lots of pollution if sensor input is incorrect or absent altogether.

One of the other sensors delivering input to the ECU is the camshaft position sensor which delivers the camshaft’s position. It is a delicate housing with two wires and a sensor head that delivers a control mechanism that synchronizes the fuel injector and the coil firing sequence.

What are camshaft position sensors?

New Camshaft Sensor

The camshaft manages the position of the exhaust and inlet valves. These valves allow fuel-air mixtures to enter the cylinder at the correct time and exhaust burnt gases at the correct time. If the valves open too soon or close at the wrong time or fuel is injected at the wrong time, the engine will not operate efficiently.

While the camshaft controls these valves, the ECU controls when to inject more fuel into the cylinders and when to ignite the gas. Knowing exactly what position the camshaft is in at any given time is the job of the camshaft position sensor. It is located near the camshaft’s ring gear.

It’s also known as the “Hall effect sensor,” and its purpose is to give off an electrical signal based on the position of the trigger wheel. Plus, it detects the direction and strength of the magnetic field, and helps the onboard computer identify the top dead center (TDC) position.

These sensors send this information to the ECU, which in turn uses this information to know when to inject fuel and air mixtures at the correct time. The ECU also receives information about the location of the crankshaft in addition to the sensors input.

Plus, together this information is used by the ECU to understand when to inject fuel, initiate sparks, and manage a host of other functions.

What does a camshaft position sensor do?

The camshaft position sensors monitor the position of the camshaft and send this information to the ECU. Knowing the position of the camshaft tells the ECU the position of each valve on each cylinder for both intake and exhaust valves.

Based on this input and that of the crankshaft sensors, the ECU will establish injector synchronization and manage the injection of gas for each cylinder as the piston arrives in the correct position.

Fuel is injected when the solenoid valve for the injection system is actuated. Valves are closed, and the combustion pushes against the piston, delivering power to the engine.

Each cylinder must fire at the right moment to deliver maximum power and efficiency. If the camshaft sensor is unable to deliver information about the location of the camshaft, the ECU cannot control the delivery of air efficiently, potentially causing acceleration issues.

Symptoms of a Failing Camshaft Position Sensor

Camshaft position sensors usually last the lifetime of the engine; however, they can fail for several reasons. Wear and tear caused by exposure to extreme weather elements, overheating, and water damage causing a fault in the electrical connections. We will review some of the symptoms associated with faulty camshaft sensor problems.

#1 Problems shifting gears

If the engine is delivering insufficient power to the transmission, the transmission may not shift gears as you attempt to accelerate. The transmission may remain in a lower gear or become locked in that gear. You can shut the engine off, wait a few minutes and restart the engine to get the transmission to change gears. This is only a temporary solution.

If the situation is difficult enough, the ECU may place your car in Limp Mode. This mode prevents your car’s transmission from shifting gears or accelerating above a specific speed. This mode will be sufficient to get you home or to a mechanic. It is not suitable to attempt to drive your car on high-speed roadways.

#2 Check engine light illuminates

One of the first indicators is the illumination of the check engine light. Although the check light could be turned on for a variety of issues, combine this symptom with some of the others mentioned in this section to narrow down the cause.

In addition, check the error codes by using an OBD2 tool to read the error codes or arrange for your mechanic to check the status of the error codes and the specific problem indicated. Ignoring the issue can permanently damage your engine. Inspect the connections to the sensor and the wiring harness for any signs of damage.

#3 Bad fuel mileage and performance

The ECU manages the engine performance to deliver maximum power, fuel economy, and emission control. When a sensor fails, the ECU’s ability to meet these goals is in jeopardy. A failing camshaft sensor may cause gas to be injected at the incorrect time and not fully consumed during combustion due to late spark delivery.

Performance suffers, and unburnt fuel is ejected into the environment. You may also encounter poor fuel mileage since the ECU is injecting more gasoline into the system to generate the power needed by the driver.

The check engine light should illuminate. Check the error codes to find out the cause of common symptoms.

#4 Problems with the ignition timing

The engine timing for injection of fuel and initiation of the spark is critical at all times, including starting your engine. If the sensor is not providing information about the position of the camshaft, the ECU cannot identify when to initiate the fuel injection nozzle to inject fuel and to ignite the fuel and air mixture.

You may have difficulty starting the engine, or it will not start at all. Check the error codes generated by the ECU to figure out the root cause of the failure for your engine to start. Confirm there is sufficient gasoline in the tank and that the fuel pump is operating.

#5 Car Starts to Jerk or Surge

If the timing is off due to a gradually failing camshaft position sensor, the ECU will not be able to know the exact timing to inject fuel and to cause combustion. The engine may sputter and/or surge in power, causing your car to jerk or surge forward as the transmission receives power from the engine.

The incorrect amount of gasoline and bad timing for the spark to ignite the fuel to air mixture can be caused by poor data signal received by the ECU from the sensor. Your check engine light should be illuminated in this situation. Check it immediately to figure out the error code and the proper solution?

#6 Poor acceleration problems

Another indication that it is failing or has failed is poor acceleration. While poor acceleration can be caused by many different issues, if the sensor is not reporting the position of the camshaft, the ECU cannot accurately determine when to cause the fuel injectors to operate and when the spark should be delivered to the combustion chamber.

Your vehicle may not accelerate past 30 miles an hour or go into limp mode, as previously discussed. Misfires, the smell of gasoline, poor combustion all are indicators of a faulty camshaft position sensor.

#7 Car Cranks and Won’t Start

Whether you are driving a car with a push-button starter or key start, if the engine cranks but does not start, there can be several reasons causing the problem. If the check engine light is on, have the error code read to determine what the issue is. Faulty camshaft position sensors, clogged fuel filters, failed fuel pumps, and other issues can cause a car to not start.

Avoid cranking your car for too long. You may drain the battery or cause the starter motor to overheat, leading to further problems. Check these conditions and eliminate those that do not have an impact on the engine start.

#8 Control unit gets blocked

In some cars, the ECU may trigger the engine to go into limp mode, which limits the speed that the vehicle can be accelerated to. This mode is meant to protect the motor and the components until repairs can be made. Your mechanic will check the error codes reported by the ECU and take appropriate corrective action.

The sensor may have failed or been operating intermittently due to poor electrical connections that have become corroded or damaged by wear and tear.

#9 Mechanical Problem

The car may be jerking, accelerating slowly, or in limp mode due to a failed camshaft sensor. There may be a mechanical problem at first due to the erratic nature of the motor and transmission operation. However, it is due to incorrect fuel injection and/or poor spark timing.

The ECU is unable to manage these functions if it is not receiving accurate information regarding the camshaft position. The dashboard light may also be illuminated. Have a mechanic check the error codes to diagnose the cause and make repairs as required.

#10 Internal short circuits

Occasionally water and oil may penetrate the device. In extreme environments, the wiring harness connecting the camshaft position sensor to the ECU may also corrode, or there is a poor connection. Either way, the ECU is not receiving the information needed to control fuel injection and spark delivery to ignite the mixture at the correct time.

Check the error codes reported by the ECU. Inspect the connections and replace the camshaft position sensor if the unit appears damaged or corroded in any way.

Camshaft Position Sensor vs. Crankshaft Position Sensor

The camshaft position sensor monitors the position of the camshaft and reports this information to the car’s computer system (ECU). The crankshaft position sensors are used to detect the position of the pistons and the crankshaft.

More so, they are both electronic sensors or devices and deliver the signal with the information concerning the positioning of either the camshaft or the crankshaft to the Vehicle’s Engine Control Module or ECU.

The camshaft sensor is used to manage the timing of the fuel injection and the generation of sparks to run the motor. It is located near the camshaft. Engines may have up to four sensors. They usually get damaged due to wear and tear and water damage.

Plus, the crankshaft position sensor manages ignition timing. The crankshaft sensor is located near the crankshaft, and each engine usually has two sensors.

Most sensors last the lifetime of the vehicle. However, they do become unusable and require replacement to return your vehicle’s engine to normal. Also, they can fail because of overheating or electrical problems.

Without the information provided by these sensors, the engine cannot run and provide the power needed to accelerate. The ECU must have these data inputs to function properly and control the operation of your motor and its components.

Camshaft Position Sensor Replacement Cost

A car driven in a normal manner, avoiding extreme conditions, and well maintained should find that the sensor will last the lifetime of the vehicle. These are electrical devices that occasionally fail due to water damage and overheating of the engine and components.

Car owners should make arrangements to have the car issues diagnosed, and replacement of the sensor before more serious issues develop caused by the defective camshaft position sensor.

The camshaft position sensor replacement costs vary depending on the make and model of the vehicle. However, the cost should range from approximately $220 to $500. Some engines are equipped with two position sensors. It is recommended that both be replaced at the same time to avoid requiring multiple visits to your mechanic for diagnosis and service.

Replacement should include diagnosis of the issue, a check for the error codes generated by the ECU, wiring harness inspection, and physically replacing the sensors. This is not a difficult job on most vehicle engines. Your mechanic should also check the coil firing sequence and variable valve timing.


The following are answers to some frequently asked questions from our readers.

Can you replace the camshaft position sensors yourself?

Many do-it-yourself mechanics replace the sensors themselves. Before beginning, use a code reader to read the error code generated by the ECU to confirm the replacement of the sensor is needed.

Always disconnect the negative battery cable before beginning any work on your motor. Locate the sensor, which is often on the engine block or cylinder head. Remove the electrical connector and the mounting screws. Pull it straight out.

Install the new sensor aligning the bolt flange with the mounting hole. Install the mounting screws and reattach the electrical connector to the camshaft position sensor. Reattach the negative battery cable and test drive your vehicle. Recheck all error codes generated by the ECU.

How do I know if my camshaft sensor is bad?

The following symptoms suggest a replacement: poor fuel economy, stalling, rough idling, hesitation, poor emission test results, the smell of gas, the car cannot start, engine misfires, the transmission does not change gears, or the check engine light is on.

If the check engine light is on, check the error code generated by the ECU unit. Error code P0340 in the powertrain control module indicates a “Camshaft Position Sensor “A” Circuit Malfunction.”, which includes the wiring harness and the powertrain control module. Check the condition of the wiring harness and the connector. If these are in good condition, it is likely to be damaged.

Can I drive with a bad camshaft position sensor?

Driving with a failing camshaft position sensor is not recommended. Take your car to a mechanic for diagnosis and repair before any significant damage can be caused by misfires, jerking of the engine, and drivetrain.

Some cars will default to Limp Mode, which allows the vehicle to be driven at low speeds. Drivers may be able to take their vehicle to the closest mechanic for service.

Driving on the highway in limp mode or very slow because the car cannot accelerate is not recommended. It is unsafe to drive on highways at slow speeds, with cars approaching at high speed.

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

The cost to replace a failing camshaft position sensor should range from approximately $220 to $500, including labor costs depending on the make and model of the vehicle and how many camshaft sensors are installed on the vehicle’s motor. Some vehicles will have two units installed.

Mechanics should read the error codes generated by the ECU, inspect the wiring harness and install the new camshaft position sensor as required. The error code indicates there is a malfunction with the cam sensor, which could also be an error caused by a bad wiring harness or a poor connector.


Often the first indication that there is a camshaft sensor problem is when your car begins to idle poorly, fails to accelerate or even start, and gas consumption increases.

Repair and replacement should be completed before damage is caused to the transmission. Drivers may notice their vehicle going into Limp Mode, which limits the top speed of the vehicle. A failed cam sensor can create unsafe driving conditions.

Drivers are recommended to have their vehicle checked immediately and repaired to avoid dangerous driving situations and also damage to individual parts such as the transmission. For more information about replacement parts, check out our categories tags down below.

Last Updated on: January 11, 2023

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