7 Symptoms of a Bad Camshaft Position Sensor (and Replacement Cost)

The camshaft position sensor (CMP) is just one of the many electrical parts found in a vehicle. We’ll go over what this component is, the symptoms of a bad camshaft position sensor, and what you can expect its replacement cost to be when it’s faulty.

A lot of people confuse the camshaft position sensor with the crankshaft position sensor because they sound similar. But there’s a big difference between the two as they perform different functions in the vehicle and have different symptoms when something goes wrong with them.

What is a Camshaft Position Sensor?

what is a camshaft position sensor

Every modern-day vehicle has a camshaft position sensor. This sensor is a very important part of any vehicle because it helps ensure that the engine is running properly.

You may have trouble spotting the sensor when you look under the hood of your car. Usually, different car manufacturers will have their own unique spot near the engine for mounting the sensor. You may find it either in back of the cylinder head, in the lifter valley of the vehicle, or next to the engine block.

The purpose of a camshaft position sensor is to determine the position of the camshaft as it relates to the crankshaft. This data is then sent to the powertrain control module (PCM) for use with fuel injector and/or ignition system control.

Common Symptoms of a Faulty Camshaft Position Sensor

#1 – Check Engine Light Illuminates

check engine light on

When your camshaft position sensor is faulty or starts having issues, the first thing you should notice is that your “Check Engine” light comes on in your dashboard. Obviously, the “Check Engine” light could indicate a variety of problems and not necessarily a bad camshaft position sensor.

In this case, you should either use an OBD2 scan tool to retrieve the stored diagnostic trouble code(s) in your car or have a professional mechanic perform an inspection of the vehicle’s engine control module to see what is going on. They too will scan this module in order to receive a series of error codes which will indicate to them what the real problem is.

Please do not ignore or postpone scanning your vehicle or getting it inspected when your Check Engine light turns on or else your engine could end up getting seriously damaged. The engine could even end up failing altogether, which means you’d end up having to either rebuild or replace your engine.

#2 – Ignition Problems

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

#3 – Car Jerking or Surging

car jerks when accelerating

If you are driving your vehicle and the camshaft position sensor starts failing, the engine will at times simply lose power and cause your car to jerk or randomly surge forward. These are both a result of an improper amount of fuel being injected into the cylinders since the PCM is getting incorrect information from the camshaft position sensor.

#4 – Engine Stalling

An even worse scenario than not being able to start your car is that your engine actually shuts off or stalls while you’re driving because the fuel injectors aren’t being told to inject fuel into the engine cylinders. We probably don’t need to tell you how dangerous that situation could be.

#5 – Poor Acceleration

reasons and causes of car not accelerating

Aside from jerking, your vehicle won’t be able to accelerate very fast when your camshaft sensor begins to fail. Heck, you’d be lucky to accelerate past 30 miles-per-hour in some cases. The poor acceleration is again due to incorrect fuel delivery by the injectors.

#6 – Problems Shifting 

Certain models of cars with a bad camshaft position sensor will end up with a locked transmission that stays stuck in a single gear. The only way you’ll be able to get out of that gear is to shut off your engine, wait a bit, and then restart. This is only a temporary solution and the problem will reappear so replacement of the sensor is necessary as a permanent fix.

Along with this, your vehicle may put itself into “limp mode” which won’t allow you to shift gears or accelerate beyond a certain speed.

#7 – Bad Fuel Mileage

This is the opposite of not delivering enough fuel to the engine. In this case, because of an inaccurate reading from a bad camshaft position sensor, more fuel than necessary is injected into the engine which causes your fuel economy to drop.

Camshaft Position Sensor Replacement Cost

camshaft position sensor replacement cost

To replace a camshaft position sensor, you can expect to pay anywhere from $120 to $300. Parts alone will run about $50 to $200. Labor costs will be in the range of $70 to $100 for professional replacement.

Expect to pay more if you have a luxury vehicle or are having your local car dealership perform the replacement. There will also be additional fees and taxes added on to these costs as well.

Can You Replace a Camshaft Position Sensor Yourself?

Yes. This is one of those jobs that almost anyone can do and is an easy way to save yourself the minimum labor fee (often close to $100) that a repair shop or dealership will charge you. It should take about 5-10 minutes to replace it.

How to Replace a Camshaft Position Sensor

  1. 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 senor.
  7. Install the new camshaft position sensor and secure with the mounting bolt.
  8. Reconnect the wire connector to the sensor.
  9. Reconnect the negative battery terminal.

Tip

When you bring your vehicle in to a dealership or repair shop for routing service or a tune-up, the mechanic won’t normally inspect the camshaft position sensor if they are not asked to.

If you have experienced any of the warning signs listed above, let them know you think it may be the camshaft position sensor. This will allow them to quickly inspect the camshaft position sensor to determine whether it’s causing these problems.

 

Comments

  1. I have just replaced top gasket and had the check light come on thinking it was bad cam timing I advanced the cam two teeth. The car pulled better but still had the light on I have replaced the cam sensor as the old one was definitely faulty but now still have the light on would the cam timing been changed cause this ???

    • This would cause it yes. The cam is out of time with the crank shaft.

      You will need to turn the light off now though. If the timing is correct, the light will stay off.

  2. my Elantra 2002 when starting immediately shoots to 2500 rpm and stays there constantly. I put it in drive and then when I pull away it will not shift gear until it reaches 4000 rpm. Could this be the cam sensor? The Hyundai dealership just changed my throttle sensor thinking this was the solution but it was not.
    Thanks. Ant

    • Throttle position sensor would have been my guess too. Check the MAF (mass airflow sensor) as well to see if it’s dirty and listen for any vacuum leaks in the engine bay. Camshaft sensor is possible.
      The late shifts could be unrelated. Transmission fluid level is fine? Have you scanned it for any trouble codes?

    • Yes, the check engine light has to be reset with a scan tool. Any mechanics shop can do this or you can buy your own tool and do it yourself. But if the problem is actually fixed, if you drive around long enough the light will sometimes reset itself if the onboard computer rechecks the area and this time discovers no fault. For some cars, disconnecting the battery for a few minutes may also reset the light.

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