There are a number of symptoms that can point to your Crankshaft Position Sensor failing but can also be confused with the same symptoms caused by issues with your ignition or fuel injection systems.
If you think your sensor has failed, here are some common symptoms of a failed crankshaft position sensor. Many of these issues may point you in the right direction:
As the engine speeds up, there needs to be adjustments to spark timing and fuel injection. Without accurate input from the crankshaft position sensor, the ECU can not make these adjustments as well as it should. This causes poor acceleration and makes your car fail to maintain constant speed.
Reduced Gas Mileage
Without accurate timing information fuel injection will have incorrect crankshaft position sensor readings leading to spark timing and fuel injection errors. The end result will affect the fuel efficiency of your engine.
Lack of proper spark timing can cause a different problem: one or more of the cylinders may misfire. That is to say combustion may be disrupted. You will feel, and maybe hear, this as a brief stutter in the engine.
You might feel that the engine runs rough or vibrates at idle, say, when you’re sitting at a red light. This is similar to the above in that it stems from poor spark timing.
Stalling and Backfiring
Another sign of a Crankshaft Position Sensor Failure is the constant stalling and backfiring of the engine. In such a scenario, the engine is prone to stalling as you drive. Unlike ignition malfunction, the car will probably start, even run for a while, only to shut down again. It goes the same for engine backfiring. If you keep ignoring the warning signs though, the engine may get exhausted and die out.
Difficult Starting or No Starting
It might be hard to get your engine started without the fuel it needs or without proper timing. If the crankshaft position sensor has failed completely, and isn’t sending a signal to the ECU at all, then the computer won’t send any fuel to the injectors. This will leave you unable to start the car.
Check Engine Light
A Crankshaft Position Sensor Failure may cause the check engine light on your dashboard to come on. A diagnostic scan tool could show any of the following codes:
- P0335 Crankshaft Position Sensor A Circuit Malfunction
- P0336 Crankshaft Position Sensor A Circuit Range/Performance
- P0337 Crankshaft Position Sensor A Circuit Low Input
- P0338 Crankshaft Position Sensor A Circuit High Input
- P0339 Crankshaft Position Sensor A Circuit Intermittent
The check engine light doesn’t always come on, though, so you could be experiencing any of the above symptoms for some time before you see the warning light.
Voltmeter or Multimeter Testing
Of course, not everyone has access to a scan tool (although they can sometimes be rented from parts stores). A multimeter or Voltmeter is a more common tool and a very useful one for diagnosing many electronic components in your vehicle. A multimeter or voltmeter can measure voltage, current, and resistance.
You can remove the sensor, and then test the resistance. Attach one end of the multimeter or voltmeter to each wiring lead of the sensor. Resistance of zero means that the there is a short circuit. Infinite resistance means there is an open circuit. Either one of those readings indicates that the sensor is not working. For any other reading, check it against the manufacturer’s specifications. If your reading is not close to the recommended resistance, then you should replace the sensor.
Another way to test the crankshaft position sensor with a multimeter is by checking the output voltage with the engine cranking.
You will need an assistant to do this. Be very careful around moving parts as you do this. Probe the wiring connectors and measure the output voltage in AC millivolts. Typically, this reading is around 200 millivolts, but this can vary from vehicle to vehicle. Check the manufacturer’s specifications. If there is no output voltage, then, obviously, your sensor is not working.
If your test results are within specifications, check the sensor electrical connector and wiring harness. It is common for loose connectors or broken wires to keep the sensor from communicating with the Engine Management System (EMS). Also, make sure to check the trigger wheel. The wheel, located on the crankshaft or damper, may have missing or damaged teeth. Any of these parts or components may trigger a CKP sensor or circuit trouble code.
These tests will help you pinpoint the source of your problem. They may help prevent you from making a repair you don’t have to, or confirm that the repair you’re about to make is the one you really need. If the testing has indeed confirmed that your sensor has failed.
Why do I no longer have a distributor ?
The advantage of having a crankshaft position sensor in your car is that you can make do without a distributor, which means less moving engine parts that break down. It is important to have your car checked by a professional auto mechanic when you experience symptoms like engine sputtering, increased fuel consumption, engine stall, and difficulty in acceleration.