Unless you’re an automobile aficionado, you probably couldn’t explain what a crankshaft position sensor is. You might not have even heard of it before.
For many people, they don’t discover what it is, or how important it is, until it’s too late.
In many cases, the vehicle starts to dip in performance, prompting owners to take it to a mechanic to see what’s going on. Others ignore the problem until it gets worse.
When your engine dies, and the car won't start, it’s definitely too late.
Waiting this long can be a costly mistake, as you’ll be stuck with your broken-down car in the repair shop, and this is the worst time to really find out about a crankshaft position sensor.
What is a Crankshaft Position Sensor?
It’s quite a mouthful to say, but this common component of modern engines is just a small little instrument. Its primary function is to monitor and track the position and the speed of the crankshaft.
In many modern cars, there is an onboard computer system that performs many central control functions. This system uses the data from the sensor for several tasks, such as maintaining engine functions and ignition times.
The standard position for the sensor is either on, or nearby the crankshaft. It transmits data to the computer to let it know the current speed the engine is running at. The control unit needs this information to improve the efficiency of the spark plugs, triggering them to ignite the fuel at the right time. It may also use the information to optimize the fuel injection times.
The crankshaft position sensor is a very common part in modern engines and can be found on basically every engine that operates with a non-distributor ignition system.
In some vehicles, there is also a camshaft position sensor, which makes it possible for the engine’s onboard computer to monitor the camshaft position. The camshaft opens and closes the valves in the engine, so being able to monitor the position facilitates greater precision and enhanced ignition management.
Despite being such an integral component, the crankshaft position sensor is rarely listed as a routine maintenance item. More surprising still, is the fact that they are susceptible to failing without any warning.
If you’re doing a lot of miles on a regular basis, it’s a smart move to replace the sensors regularly, before disaster strikes. The price will vary, taking several factors into consideration, such as the shop, the age of the vehicle, and the engine.
What tricks a lot of people is the fact that a failing sensor won’t always trigger your engine light – somewhat of a double whammy, that pulls the rug from under your feet. If you think your sensor needs to be replaced, make sure the professionals do a check with a multimeter or diagnostics scanner before taking action.
How to Know if the Crankshaft Position Sensor Needs Replacing
When it comes to engine management calculations, the position and speed of the crankshaft are critical parameters. Without an accurate signal from the sensor, the engine may not be able to run.
If the crankshaft position sensor fails, the onboard computer won’t be able to set the ignition timer, which could stop the car dead it’s already running, or make it refuse to start at all.
One of the main reasons the sensors fail is because of excessive heat, but it can also be caused by faulty electrical wiring or connections. When problems do arise, you’ll notice a few symptoms.
This is the most likely problem to occur if the sensor is poor or failing. The fundamental role of the sensor is to send information about the speed and the position of the crankshaft to the computer, so it can start the car.
If the sensor is having trouble, the computer will have trouble, which means the car will have trouble starting. Pretty simple.
Another common issue is that the vehicle may suffer from intermittent stalling.
Typically, this will occur if there are problems with the wiring or electrical connections, as the signal will be disrupted during driving. While wiring is often the problem, it’s worth checking the sensor too when this problem arises.
The Check Engine Light is On
If the Check Engine Light comes on, you may have an issue with the signal coming crankshaft position sensor. However, there are plenty of other possible issues that can trigger this light, so don’t panic just yet until you know what the problem is. It might not be the sensor. It could be something minor. (Or even something much worse!)
If any of these symptoms occur, or you have another reason to believe there is a problem with the sensor, then don’t hesitate to get it looked at. The sensor is a critical part of your engine, and is integral to performance and functionality.
It’s best to have it inspected by a professional, but if you know enough about cars, you can actually do the job yourself. It’s actually not as difficult as you may think.
What You'll Need:
Step 1 – Take Safety Precautions
In case you missed out on electrical class, let’s just remind ourselves that sensors attached to wiring involve potential harmful electricity, especially when they’re attached to a powerful car battery. You don’t want to blow yourself away on this job, so start off by taking that possibility completely out of the equation.
Disconnect the battery by removing the negative ground cable before you do anything else. This ensures there will be no sorry accidents that cause damage to the car or anyone working on it.
Step 2 - Find the Crankshaft Position Sensor
Now, with your health no longer at stake, we can get to work. You need to locate the troublesome device. The crankshaft position sensor can be affixed in various locations, depending on what make of car you are operating on.
Grab your trusty vehicle manual to find out where it’s hiding, saving yourself the hassle of searching randomly.
To give you a hint, it’s usually somewhere near the frontside of the engine, close to the main pulley. But that’s not guaranteed, as other manufacturers like to get creative with their engine design.
Step 3 - Remove the Sensor
Found it yet? Awesome. Now you have to get it out of there. No doubt you’ve already noticed that the sensor is held securely in place by some wires and a bolt.
You can pull the wire harness free from the sensor – after double-checking that you have definitely disconnecting the battery properly.
When you do this, pay close attention to the order of the connections, as you’re going to have to reattach them later. You don’t want to mess this order up, so it’s best if you get your phone out and take a clear picture of the setup prior to disconnecting the wires.
After you’ve pulled the wires out, grab the socket wrench and remove the bolt. You can then take the faulty sensor out.
Step 4 - Install your New Crankshaft Position Sensor
With the busted one out, you can put the shiny new sensor into its slot. Also, don’t forget this part:
The sensor is actually sealed to the engine interface by a mechanical gasket, commonly called an O-ring. A new sensor requires a new O-ring. So, as you’re replacing the sensor, put the new O-ring around it.
Then, reconnect the wires in the same order as before. The whole unit should lock back into position without much effort. However, if you do need to adjust it a little more, you can use a little paper spacer to correct it.
Keep a Close Eye on the Engine
Replacing the crankshaft position sensor is not a big job, but the component plays a huge role in the functionality of your vehicle. Take care when you are replacing it to make sure you have the battery disconnected for safety. Also, make sure everything is replaced as before, with the inclusion of the new sensor, of course.
Once it’s installed, reconnect your car battery and you should be good to go.
Keep a close watch on the performance of the vehicle afterwards, paying attention to how it starts up. If you notice persistent issues starting or stalling, then it may be best to take the vehicle to a professional mechanic to check it for other problems.