Crankshaft Position (TDC) Sensor

Note: For 86 and 87 cars, two types of speed/reference sensors were available:
1. Two sensors in the bellhousing, or
2. One combined sensor at the vibration damper).
Inspect the vehicle to determine which system is used, and test accordingly. Each car will have one type of sensor or the other (not both).

Cars with separate speed and reference sensors mounted in the bellhousing:

The crankshaft position sensor is mounted on the front of the engine, above the vibration damper. The sensor gets its signal from a small raised button on the vibration damper, and transmitts this signal to the diagnostic connector in the engine compartment. The crankshaft position sensor is only used for checking the ignition timing from the diagnostic connector, and not for any ECU functions.

Cars with the Pulse transmitter mounted on the front of the engine:

The crankshaft position sensor is an inductive pickup on the #1 spark plug wire. The socket in the diagnostic plug, used for checking ignition timing, gets its signal from this pickup, which produces the same signal as the crankshaft mounted sensor on other models.