Normally, resetting your crankshaft sensor requires the help of a handy tool called a scanner. This is what’s used by professionals to reset your sensor at the auto repair shop. Fortunately, there is a way to reset the crankshaft sensor on your own.
If you’re interested in learning more about crankshaft sensors, what they do, why it’s dangerous to stop one from resetting, and how you can make your crankshaft sensor relearn your vehicle without a scanner, read on.
What Does a Crankshaft Position Sensor Do?
The crankshaft position sensor (CKP) provides the ECM/PCM with input on the precise position of the crankshaft (note the missing tooth in the analog pattern and the spaces in the digital pattern), and measuring the rotation speed of the crankshaft. This information is used for injector pulse timing and ignition timing.
If you listen to an injector with a mechanic’s stethoscope when the engine is idling, and then have someone slightly increase the engine speed, you’ll hear the cadence of the injectors increase along with the speed of the engine. This is because the crankshaft sensor signal frequency increases with engine speed and the injector pulses correlate directly with the input.
Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.
Pro Tip: The pulse width of the injectors (how long the injector is open on each pulse) is calculated based on load, temperature, etc. and all this happens very rapidly because it has to.
Does Disconnecting the Car Battery Reset Your Crankshaft Sensor?
Disconnecting the car battery from your vehicle does not reset your crankshaft position sensor (although this can still depend on the vehicle). Your engine control module will reset all of its code, but this is not the same as resetting and relearning a crankshaft sensor. If your crankshaft sensor is completely broken, then no amount of resetting will fix it. Your best option is to replace it.
Why Is It Important For A Crankshaft Position Sensor to Relearn Your Vehicle?
“Crank learn” information helps the ECM/PCM detect misfires, which is important.
The crank sensor is the basic input the ECM/PCM uses for ignition timing and fuel injection. If there’s no crank sensor input, there’ll be no ignition and no fuel injection. This means the vehicle won’t even start. “Crank relearn” is only necessary on OBD2 vehicles (vehicles newer than 1996 model) with few exceptions.
The crank sensor is the basic input the ECM/PCM uses for ignition timing and fuel injection. If there’s no crank sensor input, there’ll be no ignition and no fuel injection. This means the vehicle won’t even start. “Crank relearn” is only necessary on OBD2 vehicles (vehicles newer than 1996 model) with few exceptions.
–Richard McCuistian, ASE Certified Master Automobile Technician
In terms of clearing the old crankshaft relearn snapshot and enabling the PCM to create a new one, keep in mind that every OEM PCM handles crank relearn a different way. GM even factors in bumpy road surfaces on the fly when using the crank learning comparison.
The ECM/ PCM’s algorithms are programmed to store and update the crank relearn even if it has been cleared because federal OBD2 regulations require misfire monitoring. The engine controller (ECM/PCM) can’t monitor misfires without the baseline snapshot.
For more technical information about crank relearn, read out discussion about cylinder misfires.
Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.
Pro Tip: If crank learning isn’t done, you probably won’t even know it anyway, and it’s not a problem. The engine will still run just fine.
How to Test Your Crankshaft Position Sensor
If you spin the engine over and you have fuel injection or ignition spark, you know the crank position sensor is working. However, If you’re checking because of a no-start condition once you find out you have injector operation and spark, it’s best to consider looking for the problem somewhere else.
How to Reset a Crankshaft Position Sensor
Carrying out a crankshaft position reset is a process that’s best done by a professional at an auto repair shop with a scanner.
If you’re curious as to how mechanics can reset your vehicle’s crankshaft sensor with the help of a scanner, here’s what the process may entail:
- The mechanic connects the scanner to your vehicle and turns on the ignition.
- All the necessary information for your vehicle will be inputted into the scanner.
- They will select the Diagnose button, then Control Unit, then Powertrain, and finally select the button that reads ECM or engine control module to run it.
- The Special function will be selected and run.
- The Cam Crank Relearn function will be selected and run.
- After using the scanner, the vehicle’s engine will be restarted.
- The mechanic will optimize your vehicle’s temperature so the crankshaft sensor can reset itself.
For those of you who’d rather learn how to reset a cr