In case you’re wondering what are the symptoms of a bad crankshaft position sensor, you may find it surprising that many signs will prove you may deal with a faulty component.
The most common symptoms of a bad crankshaft position sensor include engine misfiring and rough idling, rough or no startup, check engine light on, non-linear acceleration and poor fuel economy.
What is the crankshaft position sensor?
First, we will need to talk about the crankshaft itself. The crankshaft is converting the movement of the pistons into rotational motion. It’s running with the engine block with the help of the main bearings and the shaft bearings. Almost all the time they are constructed of metal or even forged steel.
The crankshaft position sensor is checking the position and the turning speed of the crankshaft. With the help of this information, the engine control units can decide on fuel injection, ignition periods and different engine specifications.
Depending on how sophisticated your car is, we can associate the crankshaft position sensor with a camshaft position sensor. Then we can verify the position of the pistons and of the valves.
Furthermore, the crankshaft sensor is sending information about the engine speed.
Above all, it’s one of the most important sensors in your car. It is used to control the spark ignition and fuel injection depending on the engine’s fuel. Moreover, a bad crankshaft position sensor can prevent an engine from starting.
Symptoms of a bad crankshaft position sensor
What are the symptoms of a bad crankshaft position sensor? Most common sources of a bad crankshaft sensor are the faulty electrical circuits, and damage in the sensor because of engine overheating.
1. Check engine light turned on
This is the first and the most common symptom. The issue here is that you cannot always correlate the check engine light with a bad crankshaft position sensor because other components can provoke this behavior.
However, after you diagnose the vehicle with an OBD scanner or any other diagnosing tool you can know for sure which components is causing the issue. Is always good to think on multiple sources, but a faulty crankshaft sensor can be one of them.
2. Non linear acceleration
When the signal received from the crankshaft position sensor is not correct the spark timing or fuel injection cannot be properly set. Then you feel that while you are speeding up, the car is not responding as it should.
This means that it can speed up slower than you are pressing on the gas pedal and it’s challenging to maintain a steady speed.
3. Engine intermmitent failures
We can translate this as a car jerking behavior. When you feel that your engine is misfiring, the cylinder cannot have the proper movement because of the wrong information received from the sensor.
As the engine control unit receives wrong information about the cylinder position, this will cause an engine misfire. Bad spark plugs can be responsible also for this behavior, but if you check them and they are in proper condition, then it’s likely that the sensor is faulty.
4. Vibrating engine when idling
When you are standing with your vehicle in neutral, you may hear or feel a hard idling. This symptom can also be the origin of other components but don’t exclude a worn out crankshaft position sensor.
Usually this happens because the sensor is not checking the position properly and sending wrong information.
5. Poor fuel economy
This happens when the timing in the cylinders is not correct. It injects fuel at wrong moments in time, and sometimes it’s just burned and evacuated. This means that your car is consuming more fuel for the same power output.
However, is a good idea to check whether this issue is actually from a bad crankshaft position sensor as other components like a bad O2 sensor can also be the culprit for this unexpected behavior.
6. Hard or no startup
Along with the engine light on, this is one of the most common causes. Actually, maybe the light is turned on your cluster after a failed startup.
This means that information from the crankshaft position sensor is wrong. Because of this, the crankshaft speed is incorrect, which is causing the control units to not be able to time fuel injection.
It might be difficult to start the vehicle, or even engine to stop after we started it.
Here’s something to remember
Can a car run without a crankshaft position sensor?
Some people are asking if you can drive a car without a crankshaft position sensor. Maybe these things were possible in the past, but with the modern cars it’s not the case. Let’s do a short resume of our discussion.
The crankshaft position sensor is tracking the position and the speed of the crankshaft. The crankshaft itself is driven by the cylinders movement. This means that if we don’t have a sensor to track all these parameters, the engine cannot run. When the first cylinder is in the top position, the spark can do its job, but this is signaled by the crankshaft position sensor.
So let’s we put it in a few words. If your car has a crankshaft position sensor that is sending information to an engine control unit, your car cannot run without it.
Can you drive with a bad crankshaft position sensor?
There are two options here. Maybe the sensor has an intermittent issue, and a check engine light signaled it. This means that your car still starts, but the error is on your cluster.
First you should test how your car is performing. If any of the above symptoms occur, wait until you change the faulty crankshaft position sensor.
If you feel that the care is still good to drive, then you can drive it. However, it’s wise to check if you have a loose or cut wire that is causing the issue. Even if you diagnosed your car with a faulty crankshaft sensor, it might happen that is an electrical issue.
Always check these things and then take the final decision on how to proceed.
How to test a crankshaft position sensor?
The most important thing in this case is to evaluate how many wires does your sensor has. In case of a magnetic sensor, you have two wires.
This means that while the crankshaft gear is moving, it’s inducing a voltage in the sensor’s output. This voltage is then evaluated and transduced to a rotational speed value.
Steps you can follow to test a 2 wires sensor:
- do a visual inspection on the sensor to check any deformation or abnormalities;
- place your multimeter on Ohms and check the sensor value (between the two pins) – should be around 2 MΩ;
- check the harness connecting to the sensor – pull wires and check the continuity;
- move your multimeter scale on AC voltage (around value 2) and connect the probes to the sensor;
- move a metal back and forth and check if the voltage is changing value on multimeter;
- in case you have different voltage outputs it means that your sensor is sending information;
Steps you can take to check a 3 wires sensor:
- identify the pin-out of the sensor – should have a 12V supply wire, GND (ground) wire and the signal wire;
- you will need a car battery or a 12V power supply to power on the sensor;
- it’s also a good idea to use a back probe on the sensor’s harness
- place the multimeter on DC voltage (20V scale) and try to crank your engine or move the sensor next to a metal part
- if you get a voltage between the signal wire and GND, it means that the sensor is outputting signal;
I will leave you a video below where you can see exactly the procedures described above:
Changing a crankshaft position sensor
If you don’t feel confident in doing it by yourself, find a mechanic or a specialized person. To change a crankshaft position sensor you can follow the steps described below:
- jack the car and properly secure it
- locate the sensor position – usually on the lower part of the engine – crosscheck it with the new sensor;
- take off the battery connection to avoid any short circuits you may produce;
- try to remove all the things which interfere with your job;
- take off the connector from the harness next to the sensor – it might be a bit difficult because of the seal that is preventing water entering;
- remove the bolt that is holding the sensor;
- remove the crankshaft position sensor – you might need a screwdriver;
- compare the new sensor with the one you have removed – they should have the same length, mounting hole and connector entrance;
- clean the area where the sensor is placed and mount the new sensor;
- place back the connector from the harness and check that is properly locked;
- connect back the battery terminal or terminals if you removed both cables;
Check the video below on how the action is done for a better understanding:
Can a bad crankshaft sensor cause no start?
The answer is definitely yes. If the engine control unit cannot assure a proper spark when you start the engine it will not start. It might happen that the engine cranks and turns, but that’s it.
However, it might happen that is an occasional issue and sometimes your engine can start and function without problems. This means that your crankshaft sensor is getting faulty or you have an electrical issue.
Today you found out what the symptoms of a bad crankshaft position sensor and also some additional information regarding on how to test and check a crankshaft sensor.
In conclusion, we can say for sure that many symptoms can define a faulty crankshaft position sensor, but it’s always reasonable to properly investigate the issue to fix it.