Locate the crank position sensor
Inspect the sensor, connector, and wiring for damage, corrosion, or looseness
Check the vehicle service manual for sensor type and test specifications
Disconnect the sensor connector
Test resistance across the sensor terminals with a multimeter if it is a magnetic pickup type
Compare the resistance reading to the manufacturer specification
Check for continuity between sensor terminals and ground if specified
Reconnect the sensor
Backprobe the signal wire with a multimeter set to AC volts for a magnetic pickup sensor
Crank the engine and verify an AC voltage signal is produced
Backprobe the signal wire with a multimeter or oscilloscope for a Hall effect sensor
Turn the ignition on and verify the sensor has proper power supply and ground
Crank the engine and verify the signal switches between low and high voltage
Inspect the reluctor wheel or tone ring for damage, missing teeth, or misalignment
Check sensor air gap and adjust if required by specification
Scan for diagnostic trouble codes with an OBD-II scanner
Clear codes and retest after repairs
Replace the sensor if readings are out of specification and wiring is confirmed good