If your car has a bad crank sensor, you will need to diagnose the problem in order to identify the necessary repair for starting the car. First, you should check for fault codes stored in the car’s computer. Many crankshaft sensors can produce a trouble code or even a warning light, so you should check for that first. If there are no error codes or warning messages, you will have to use an oscilloscope to measure the crank sensor signal. If the crank sensor is not producing a signal, the sensor has failed and needs to be replaced.
Once you have identified a failed crank sensor and the part is replaced, the car will need to be driven and the computer re-learned with the new sensor’s position. This means the car will need to run for at least 15 minutes to allow the computer to learn the new sensor and gain the necessary data. Finally, to enable the car to start, you will need to cycle the ignition key off and on three times, then attempt to start it as usual.