Crank Sensor

Crank Sensor – Why They Fail, How To Fix Them, And For How Much

Engines are highly complex componentry and one that has thousands of individual parts within its construct working in unison. It can include anything as large as the engine block, to the tiny mounts that keep it all bolted together. Among those parts that make up the engine unit is the crank sensor. As small as it may appear, it plays a huge role in the inner workings of your engine, and when they do fail, it could cause a lot of problems.

After all, your engine has many moving parts, which often rely on each other’s movements so that the rest of the motor can operate harmoniously. It’s the tiny electronic gadgets like the crank sensor that monitors all these motions and ensures that everything is in good order. So, what is the crank sensor, and why does it matter? Moreover, for such an apparently important component, how is it that they could fail? Well, let’s take a peek at everything you need to know about a crank sensor.

What Do You Need To Know About The Crank Sensor?

First and foremost, what is the crank sensor? It’s usually referred to by its full name, the ‘crankshaft position sensor‘. You can find this tiny little piece of the sensor positioned right around the engine block, commonly up front in the engine near the timing cover. But let’s break it down further, and discuss what the ‘crankshaft’ is, and what this sensor does in relation to it. Not to be confused with another similarly named component, the ‘camshaft’, the crankshaft sits at the bottom of the engine.

It consists of a long “shaft” that’s driven through a “crank” mechanism, hence its name. Its only role is to take in the reciprocating motion of the engine’s pistons moving up and down, which is caused by the combustion process. Then, the crankshaft can translate that upwards and downwards dance of the pistons into rotational motion. This can be fed to the flywheel, which is thus connected to the transmission. From there, your engine’s combustion power can rotate the wheels.

The crank sensor – or crankshaft position sensor – meanwhile, monitors the position and rotational speed of the crankshaft. This analysis is gathered by the engine’s electronic management systems, or the engine control unit (ECU). The data collected on how fast the crankshaft spins (in RPMs) enable the ECU to better control the fuel injection (how much fuel to burn) and the ignition system (when to ignite the air-fuel mix). Both will aid in improving fuel efficiency, longevity, and performance.

What Causes Your Crank Sensor To Fail?

So then, we can conclude the functionality of the crank sensor as being a monitoring device for your engine’s computer brain. This is important for a few reasons besides the fuel injection and ignition system, such as adjusting other engine-based parameters. It could also work alongside a few other sensors, such as the camshaft sensor. By being able to carefully monitor the crankshaft’s workings, the engine can operate more healthily. It drinks less fuel, lasts longer, and enhances performance.

But for what we can consider being a vital component of the engine, how could the crank sensor fail? Well, there are a few good reasons as to why the crank sensor can, after some time, wear out and could longer function. Here are some of the common causes for failure…

1. Extensive Exposure To Heat

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The crankshaft sensor once again is placed right in the innards of the engine. More specifically, it can be found mounted on the crank pulley, flywheel, camshaft, or on the crankshaft itself. As such, the sensor’s assembly is constantly bombarded with a significant amount of heat from the engine and its surrounding components.

The crankshaft sensor has a small circuit board inside, with some wiring and copper coils. All this is then wrapped in a plastic casing. When there’s too much heat, this build-up of temperature can cause damage to the internal circuitry. Alternatively, it could be hot enough in there to start melting away the plastic casing of the crank sensor. This will result in damage over time.

2. Faulty Wiring Harness

To transmit its monitoring data back to the engine’s control systems – the ECU – the crank sensor is connected through a wire harness. Although it’s made to be robust, given the conditions it has to work in, a failed wiring loom can compromise the crank sensor. Or, the sensor itself might still be just fine, but it won’t be able to send any data back to the ECU.

The wiring harness could be knocked free from its connection, or has been frayed and is worn down. Any debris within the engine bay, such as oil or contaminants, could eat away at the wiring after some time. In all, it could lead to the incorrect voltage being powered within the system, or result in issues with the return circuit on the crankshaft sensor.

3. Circuitry Problems

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Speaking of electrics, the circuitry inside the crankshaft sensor can also be susceptible to wear and tear. Besides, the sensor relies on the well-being of its electric and electronic components in order to send back its analysis to the ECU. Most commonly, the wiring inside of the sensor is quite vulnerable to disruptions. The wires might be damaged from an accident, for example.

Perhaps it’s been frayed and is short-circuiting, or if it’s become loose from its connectors. Incorrect – which is to say too little or too much – voltage sent through the wiring could affect the condition of the sensor, too. These can compromise the still-functioning crankshaft sensor to wear down faster and eventually leads to complete failure.

4. Damaged Wheel And Pin

Among the parts inside the crank sensor, we have the ‘wheel’ and ‘pin’. Both the pin and a toothed wheel measure the magnetic pulses collected by the crankshaft sensor. It’s from this data where it can inform the sensor on the rotational speed or positioning of the crankshaft. After a while, the pins and wheels will eventually wear out and fail.

When the wheel and pin set is compromised, the measuring of the magnetic pulse pattern could no longer be done. Or, it might be disrupted to a point where wrong measurements are collected. When this happens, the wheel and pin will send an incorrect analysis of the crankshaft’s rotational speed. This could either confuse the ECU, or it might damage the crank sensor altogether.

5. Snapped Timing Belt Or Chain

The timing belt – or timing chain – is responsible for synchronizing the movement of the camshaft up top, and the crankshaft down below. The timing belt or chain eventually needs a replacement. If it doesn’t, the extended wear could be enough to snap the timing belt entirely. Another possibility would be the timing belt or chain snapping after a collision.

When it does snap, the force could be great enough that the belt or chain wraps around the crank sensor. To have its strain be put on the plastic sensor is adequate to break it. If not, we may also consider a scenario in which the snapped belt or chain strikes the sensor at speed. Once again, this impact is more than sufficient to rattle it, or cause considerable damage to the sensor.

What Are The Symptoms Of A Faulty Crank Sensor That You Need To Look Out For?

Every single fuel-injected vehicle today – either petrol or diesel – has a crank sensor. Thus, any one of the numerous points of failure that we discussed earlier, from poor wiring to heat, can compromise it. This is concerning given how important it is to measure the speed and position of the crankshaft. Many engines today can’t run if the ECU isn’t able to determine just how fast the crankshaft spins. With that in mind, we seriously don’t recommend driving your car if you have a faulty sensor.

A defective crankshaft sensor can lead to catastrophic damage to your engine, which is by no means cheap to repair or replace. However, the crank sensor (spoiler alert) is a very cheap component by comparison. So, do make sure that you have your car thoroughly checked out if any of these tell-tale signs and symptoms of a faulty crank sensor appear…

1. Difficulty In Starting The Vehicle

If the sensor is damaged, you may have some trouble getting your car to start up. This is a reminder that the crank sensor’s data is required by the ECU, in determining the crankshaft’s position and speed. Without it, the ECU – which manages everything on your car’s powertrain – isn’t sure about how much fuel to inject into the combustion chamber, or when to ignite it.

Moreover, other parameters that are measured by the ECU regularly can’t be analyzed, as the crank sensor’s data is either incorrect or isn’t providing any information at all. It needs to talk with other components – such as the camshaft sensor – when a car is ready to be ignited. In the case of a faulty crankshaft sensor, you’ll have ignition difficulties, or the car might not start up at all.

2. Stalling Or Intermittent Engine Cutting In And Out

An extension of our previous point on the ignition, even when your is up and moving, the damaged sensor can still cause issues. Once again, the ECU can’t provide the engine with the right instructions if the crank sensor is faulty. When you’re on the move, this can be exhibited as your car stalling in the middle of the road. Or, the engine might cut in and out intermittently as you drive along.

If this does happen to you, we can usually point the finger at the wiring or electrical side of things. Maybe the wiring inside the circuitry or the cables connecting the sensor to the ECU is faulty. This then results in the sensor’s data signals being cut off when the engine is still running. Although, this doesn’t rule out the possibility that the entire crankshaft position sensor isn’t damaged.

3. Sluggish Or Jerky Acceleration

Crank Sensor

Remember the two aspects of the combustion process that relies on input from the crank sensor – the fuel injection, and ignition. Based on the rotation of the crankshaft, it’ll tell the ECU to calibrate just how much fuel you need. On top of that, it can inform the ECU on when’s the best moment to ignite the fuel-air mixture in your car’s combustion chamber.

If the crankshaft position sensor fails, it’ll provide inaccurate or incomplete signals to the ECU. This leads to poor adjustments made by the ECU in regards to the timing of the sparks, and the volume of fuel. It’ll get worse when the engine speeds increase. In other words, when you put your foot down. Consequently, you can notice a loss in performance, either felt as sluggish or jerky acceleration.

It can make it much harder for you to maintain a steady speed, as the ECU is fed either no data at all or lacks accurate signals from the crankshaft sensor. The scenarios include, for example, the ECU not injecting enough fuel to let the engine burn. Or, it might ignite – and thus combust – the fuel-air mixture at the wrong moment to deliver adequate performance.

4. Misfiring Engine Or Stuttering

Once again, a faulty crank sensor will interfere with the engine’s ability to deliver performance and power smoothly. You might be able to feel some stuttering with the engine, mostly when you’re just starting up or while accelerating. It could likely be caused by your engine’s cylinders misfiring. The exact cause of misfires is numerous, such as poor spark plug timing.

But if everything else checks out, then it might be prudent to check the crankshaft position sensor. If and when it does fail, it might not provide the ECU with the necessary data on the positioning of the pistons. Remember, the pistons’ movement affects the position and speed of the crankshaft below it. If the pistons aren’t correctly aligned, this is what leads to your engine misfiring.

5. A Rough Idle Or Odd Vibrations

Crank Sensor

When you stop at a red light, you might be able to feel that the car is vibrating more than it should. The idling is rough, as though you’re sitting on a tumble dryer at full tilt. You may also hear some odd sounds, as though the engine is grinding or rattling. While this may be due to several different causes at its core, the crank sensor is one of them.

If the crankshaft positioning sensor isn’t working, then it can’t monitor the positioning or the speeds of the crankshaft. If the crankshaft is let loose without calibration and constant control by the ECU, it could start working out of tune. This is where the vibrations might be coming from. Additionally, it might affect the engine’s performance, as well as interfering with the mileage counter.

6. The Check Engine Light Comes On

Your car has various sensors connected to the ECU. Should the ECU pick up anything wrong with any one of these sensors, it will warn you about it. We can sometimes see error messages pop up in the dash, or have warning lights blaring at us. One of them is the ‘check engine’ light’, which illuminates if there are faults within the engine. This includes any problems with the crank sensor.

Often, the ECU might be smart enough to sense that something in the signals sent by the sensor is off. Perhaps the readings aren’t right, or if the ECU can’t get any information out of the crankshaft position sensor at all. In this case, the vehicle’s ECU will light up the check engine light as a warning to you. It’s wise to get this diagnosed, just to see what’s exactly triggering the light to come on.

7. Poor Fuel Economy

One of the advantages of a properly functioning crank sensor is improved fuel efficiency. It’s possible because it can tell the ECU exactly how much fuel to inject into the combustion process. No more, no less. If the sensor fails, it can’t provide accurate signals to the engine pertaining to the information on the timing. Particularly, how much fuel to use, and when to time the ignition just right.

Now, the fuel injectors can’t pump fuel into the engine effectively. It could provide too much fuel to burn, or not enough. The ignition might be off-key as well, igniting the fuel-air mixture too early or late for the combustion to be done efficiently. This leads to the engine’s fuel economy plummeting over time, as it’s consuming more gasoline or diesel than is actually necessary.

How Can You Diagnose A Faulty Crank Sensor?

So, let’s say that you’ve encountered one or more of those aforementioned symptoms… How could you diagnose your car to make sure that the blame lies on the crankshaft position sensor? The most convenient option is to head down to a workshop, and let the technicians check it for you. However, you could opt to do it yourself. If you have an OBDII diagnostics tool at home, you can plug it into your car to scan and read out all the error codes.

The ECU can spew out error codes for a faulty crank sensor that’s similar to emissions-related faults. It will vary depending on the make and model of your vehicle. So, look out for any of these codes below, to narrow down the potential cause as a defective crank sensor:

  • P0315
  • P0335-P0339 (More specifically, codes P0335 to P0338 can point directly to crank sensor issues)
  • P0385-P0389
  • P0016-P0019 (This is for the camshaft sensor, just for reference)

If the error codes aren’t displayed clearly, you can use the tactic of running the engine while reading the OBD diagnostics tool. There should be a setting that enables the OBD reader to show you the engine speed in RPM (revolutions per minute). That scanner of yours will be getting the engine speed reading from the crankshaft position sensor.

So, set up the OBD reader to read the engine speed in RPM, and then start up the engine. Normally, the scanning tool should read you somewhere between 100 to 500 RPM, although this might vary from vehicle to vehicle. If the scanner gets a bad reading, say less than 100 RPM, then the crank sensor isn’t working properly. Should you see a 0 RPM reading, then the sensor may have failed completely.

How Much Is For A Crank Sensor Replacement Cost?

Unfortunately, the crankshaft position sensor isn’t a component that could be easily repaired if it’s gone awry. On the bright side, the cost of a replacement isn’t too high, either. For most cars, you can complete a crank sensor replacement for around $120 to $300, in parts and labor. The sensor itself will only set you back between $75 to $120, which you can find on most auto parts store shelves. You may like to consider saving a few dollars with a used, but still perfectly functional sensor.

Nonetheless, a brand new sensor could at least guarantee that it’ll work properly out of the box. On the flip side, the labor charges – if you choose to have a technician replace it for you – will add to about $45 to $180 for an hour or more to get the job done. Overall, the cost of a replacement crank sensor isn’t too terrible, especially given what happens if you don’t replace it promptly. A brand new engine, should things go south really quickly, could cost you a few thousand more.

Crank Sensor – Conclusion

Well then, that rounds up our look at the humble crankshaft position sensor. It plays a crucial role in the daily workings of your engine. It ensures that the engine could last longer, while also efficiently managing fuel consumption and performance. Yet, the crank sensor can fail as it wears out, which may lead to numerous other problems if not diagnosed and replaced promptly. At the very least, this is one automotive problem that doesn’t cost an arm and a leg to replace.

This expense is a very small fraction of how much it would otherwise cost to cover one’s ignorance if they fail to act in replacing a faulty crank sensor. Apocalyptic engine damage is more than possible should this sensor not be replaced in time. At the very worst, the engine could fail entirely, all of it because of a single sensor. It highlights just how important it is that the engine’s many moving parts work seamlessly with one another. The crank sensor, among others, makes certain of that.

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