What Is a Camshaft Position Sensor And What Does It Do?

Your car has many different sensors, including one or more camshaft position sensors. Although camshaft position sensors are designed to last the life of the vehicle, that doesn’t always happen.

Over time, these sensors can degrade to the point that they produce an erratic signal or no signal at all.

If your car experiences a camshaft position sensor failure, you’ll likely notice one or more troubling symptoms that you’ll want to address right away.

What is A Camshaft position sensor?

Camshaft position sensors monitor the camshaft’s position and send information to the engine control unit about when each valve is open on a particular cylinder. They work closely with crankshaft position sensors to paint a complete picture for the engine control unit.

The engine control unit needs this data to control how much fuel enters the combustion chamber and ignition timing (spark timing) to ignite the fuel, when the air-fuel mixture is ignited simultaneously, engine performance increases, fuel consumption, and tailpipe emissions decrease.

In modern auto-start/auto-stop engines, the camshaft position sensor determines which cylinder is on its power stroke relative to the crankshaft position and provides fuel and spark to start the engine when you step on the accelerator pedal.

A defective camshaft position sensor can warn you before it fails and leaves you stuck.

How Many Camshaft Position Sensors Are in a Car?

A vehicle may have one or more of these sensing devices. There’s usually one cam sensor in the engine. However, some have more than one and up to four.

In principle, vehicles without variable valve timing (VVT) have one, while those with VVT have two or four. Most have two, though. Four are rare to find.

Older engines that use a carburetor system have none. In these vehicles, there’s no need for TDC determination. They include those made in the 90’s or earlier.

Where is the Camshaft Sensor Located?

The exact location varies from one engine or vehicle to another. Most modern engines have it mounted at the top near the camshaft. In some, you can find it in the engine block or other components such as the flywheel or transmission bell.

That said, you can always use your car’s manual to find the exact location of this sensing device. Knowing its location can help you check it for damage, and if you’re a DIY enthusiast, replace it if it fails.

Bad Camshaft Position Sensor Symptoms

Usually, there are a few warning signs that you may experience when the camshaft position sensor is failing. Keep an eye out for these common symptoms:

#1. Check Engine Light Illuminates.

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.

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.

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.

What Will Happen If I Ignore a Bad or Failing Camshaft Position Sensor?

If you ignore the symptoms listed here and your camshaft position sensor fails, your vehicle will not start. As a camshaft position sensor weakens, so does the data it transmits to the ECM.

Eventually the data signal becomes so weak the ECM switches off fuel and spark delivery, and your engine will not start.

This is only a frustrating inconvenience if it happens while your car is parked, but it can be a dangerous situation if your car shuts off while you’re driving.

When your vehicle doesn’t run like it used to, or the Check Engine light is on, the camshaft position sensor may need to be replaced. Eventually your engine will stop running if you disregard these symptoms.

Camshaft Position Sensor Replacement Cost

We probably don’t need to tell you how dangerous this situation could be.

To replace a camshaft position sensor, you can expect between $ 95 and $ 200. The parts alone cost between $ 25 and $ 100. The labor cost for a professional replacement will range from $ 70 to $ 100.

Expect to pay more if you own a luxury vehicle or have the exchange done by your local car dealer. Additional fees and taxes are added to these costs.

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 dealer will charge you. It should take around 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 sensor.
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 routine 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.

Is It Safe to Drive with a Faulty Camshaft Position Sensor?

Driving with a bad camshaft position sensor is technically possible but it’s not recommended. It can cause reduced engine power, stalling, rough idling, and poor acceleration. You may suddenly lose power on the highway or struggle to merge into traffic.

The emissions system can also be affected, leading to a failed emissions test. Ignoring symptoms like a lit Check Engine light could lead to catastrophic engine failure down the road.

You may assume it’s just the sensor but in reality, your car may have stored a dozen other trouble codes, much more serious, and you’d never know it.

It’s just not worth the risk. Get the camshaft position sensor replaced at your earliest convenience.

FAQs.