Locate the crankshaft position sensor
Inspect the sensor and wiring for damage, corrosion, or loose connections
Check the sensor connector is fully seated
Scan for trouble codes with an OBD-II scanner
Compare live engine RPM data while cranking
Test sensor resistance with a multimeter if specified by the manufacturer
Test sensor voltage output while cranking
Check for proper power supply and ground at the connector
Inspect the reluctor wheel or tone ring for damage or debris
Verify sensor air gap if applicable
Use an oscilloscope to check the sensor waveform
Replace the sensor if readings are out of specification