The crank angle sensor on a 1987 Nissan Sentra measures the angle of the crankshaft in relation to the engine block, and helps the engine control module, or ECM, decide when to fire the ignition. When this sensor fails, the ECM can't determine when to fire the spark plugs and the engine will not start. Replacement crank angle sensors are available from auto parts stores, Nissan dealerships and online parts websites.
Tools Used: Automotive scan tool
Test Crank Angle Sensor
Stop the Sentra and shift its transmission into park or first gear (manual). Turn off the engine and apply the parking brake. Turn the ignition switch back to the "On" position, so the dash lights are on but the engine is not running.
Plug an automotive scan tool into the Sentra's diagnostic data port. This port is located underneath the steering wheel, on the driver's side of the vehicle.
Turn on the scan tool and choose "ECM" from the main menu. Choose "Live Data" from the ECM menu, and then choose "Crank Angle Sensor."
Rotate the ignition switch to the "Start" position and crank the engine. Watch the scan tool's display; it should show the cranking RPM of the engine. If it doesn't show the cranking RPM, then the crank angle sensor is faulty and must be replaced.
Tips & Warnings
An automotive scan tool is a hand-held, portable computer unit used to perform tests on passenger vehicles. Scan tools are also used to gather important diagnostic data. They are available from auto parts stores, automotive tool retailers and online tool websites.
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