Blog Car Care Advice 8 Symptoms of a Bad Camshaft Position Sensor (+ How to Fix)
Car Care Advice

8 Symptoms of a Bad Camshaft Position Sensor (+ How to Fix)

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The camshaft position sensor (CMP sensor) ensures the engine’s valves open and close at the correct times for smooth engine performance.

But what if your vehicle shows symptoms of a faulty camshaft position sensor?
How can you fix it?

Keep reading to learn about the common symptoms of bad camshaft position sensors, why they may fail, and the steps involved in replacing a faulty sensor.

This Article Contains:

8 Symptoms of a Faulty Camshaft Position Sensor 

The camshaft sensor works with the crankshaft position sensor (crank sensor) to define the exact position of the crankshaft drive.

A camshaft position sensor malfunction can disrupt the vehicle’s fuel injection and ignition timing by sending inaccurate or delayed signals to the Engine Control Unit (ECU).

When that happens, you might notice the following signs:

1. Illuminated Check Engine Light

When the camshaft sensor fails, the Engine Control Unit detects an irregularity in the camshaft’s position data and activates the check engine light.

Note: The check engine light can also illuminate due to a bad crankshaft position sensor or other faulty components. It’s best to get professional help inspecting your vehicle to diagnose the issue accurately.

2. Engine Misfire

If a bad camshaft sensor (or a faulty crankshaft sensor, too) relays incorrect data to the ECU, spark timing will be affected. The spark plug may ignite at the wrong time, leading to incomplete fuel combustion, which results in an engine misfire or car stuttering.

3. Poor Fuel Economy

A malfunctioning camshaft position sensor disrupts the fuel injection timing, causing the fuel injector to remain open longer than required. This allows excess fuel to enter the combustion chamber, resulting in incomplete combustion and fuel wastage.

As a result, your vehicle’s fuel economy drops.

4. Diminished Vehicle Performance 

A failing camshaft position sensor disrupts ignition timing, resulting in slower responses and less engine power when accelerating. This poor acceleration makes your car feel sluggish and less responsive.

5. Transmission Problems 

A camshaft position sensor can damage your car’s transmission system by sending incorrect information about the engine speed to the ECU. This can lead to problems like mistimed gear shifts, transmission slips, poor fuel economy, and vehicle stalls. 

Note: Some cars also have a “limp-home mode”, wherein the ECU limits the vehicle’s speed to prevent transmission and engine issues. This allows car drivers to drive to a mechanic for repairs safely.

6. Rough Idle

Misfires caused by a faulty camshaft sensor and problematic spark timing can make your engine idle roughly. This rough idling manifests as noticeable vibrations or shaking in the vehicle, making the car feel less stable.

7. Vehicle Stalls or Won’t Start 

Incorrect CMP sensor data can cause your engine to behave erratically because it relies on this data to time the ignition and fuel injector operation. 

As a result, the engine may not receive the spark or fuel required for smooth and continuous operation, leading to unexpected vehicle stalling while driving or idling. It can also make your vehicle hard to start

8. Failed Emissions Test 

A bad camshaft position sensor creates an overly rich fuel mixture that doesn’t burn completely and increases harmful emissions like carbon monoxide, nitrogen oxides, etc., from the exhaust.  These elevated pollutant levels in your exhaust can make your vehicle fail an emissions test.

But what leads to camshaft position sensor failure?
Find out next.

What Causes a Camshaft Position Sensor to Fail?

A camshaft position sensor failure can happen for several reasons, including regular wear and tear.
Some common causes include:

Now that we’ve covered the symptoms and causes, let’s see how a camshaft sensor replacement is done.

How to Replace a Faulty Camshaft Position Sensor

As camshaft sensor replacement can be tricky, it’s best to have a professional handle it. 

A mechanic will first use an OBD-II scanner to read the car’s computer for error codes and check if a bad camshaft position sensor is the culprit. If the cam sensor is faulty, here’s how they’ll replace it:

  1. Locate the sensor: They’ll find the camshaft sensor, typically situated in the engine block or cylinder head, depending on your engine’s design.
  1. Disconnect the battery: They’ll disconnect the negative battery cable for safety and to prevent electrical issues.
  1. Remove the bad sensor: They’ll disconnect the sensor’s electrical connectors and remove the bad cam sensor by unscrewing the mounting screws.
  1. Install the new sensor: They’ll carefully insert and align the new cam sensor, tighten the sensor’s mounting screws, and reattach the electrical connectors.
  1. Reconnect the battery: After replacing the cam position sensor, they’ll reconnect the negative battery cable. 
  1. They’ll use the OBD-II scanner to clear the error codes and relearn the sensor to ensure it sends accurate data to the Engine Control Module (ECM).

Note: The same process is also followed to replace a failing crankshaft position sensor. 

Have more questions?
Check out these FAQs.

5 FAQs about Camshaft Position Sensors

Here are answers to some common questions about camshaft position sensors:

1. What’s the Difference Between a Camshaft and a Crankshaft Position Sensor?

A camshaft sensor monitors the position of the camshaft, which controls the opening and closing of the engine’s valves for precise fuel injection and ignition timing.

In contrast, the crankshaft position sensor monitors the crankshaft’s rotation and converts the engine’s linear motion into rotational motion. The crankshaft sensor helps the ECU determine the crankshaft’s position and the engine speed (RPM). 

2. Does a Car Have Multiple Camshaft Position Sensors?

Yes, some cars can have multiple camshaft position sensors. The number of sensors in a vehicle may vary depending on the number of camshafts in the engine.

Most modern engines have one sensor per camshaft, so cars might have one, two, or even four sensors. But, sometimes, a vehicle may have only two sensors, even with multiple camshafts.

3. How Long Does a Camshaft Position Sensor Last?

Camshafts are designed to last around 186,000 to 248,000 miles or more, but this can vary based on your vehicle’s make and model, the sensor’s quality, and driving conditions. 

They can also fail prematurely due to regular wear and tear, corrosion, engine oil leaks, etc. So you must replace them if you notice signs of a malfunctioning camshaft position sensor.

4. Is it Safe to Drive with a Bad Camshaft Position Sensor?

No, it’s not safe to drive with a faulty camshaft position sensor, as it can lead to reduced engine power, poor acceleration, or complete vehicle shutdown. 

A bad sensor can also damage other critical car parts and lead to costly engine repairs.

5. How Much Does Camshaft Position Sensor Replacement Cost?

Replacing a failing camshaft position sensor costs around $2,000 and $3,000, including the cost of parts and labor.  

However, these costs can vary depending on your vehicle’s model and local labor rates

Drive Safe and Smooth with AutoNation Mobile Service

A bad camshaft sensor can disrupt your vehicle’s smooth operation by diminishing engine performance, reducing fuel efficiency, and posing safety concerns. So, if you notice bad camshaft position sensor symptoms in your vehicle,  it’s best to get professional help. 

That’s where AutoNation Mobile Service steps in.
We’re a mobile auto repair service available seven days a week, offering upfront pricing, convenient online booking, and a 12-month, 12,000-mile repair warranty.

Contact us, and our mechanics will resolve your camshaft sensor malfunction right in your driveway! Have a bad crankshaft sensor or timing belt issues? We can help you, too.