Crankshaft Position Sensor: Operation

WARNING: This page is about a different car, the 2005 Dodge Grand Caravan, 2005 Dodge Caravan, and 2005 Chrysler Town & Country. However, it is still accessible from the selected car via links, so may be relevant.

The crankshaft position sensor detects slots cut into the transmission drive plate extension. See Fig 1. There are 3 sets of slots. Each set contains 4 slots, for a total of 12 slots. See Fig 2. Basic timing is set by the position of the last slot in each group. Once the Powertrain Control Module (PCM) senses the last slot, it determines crankshaft position (which piston will next be at TDC) from the camshaft position sensor input. The 4 pulses generated by the crankshaft position sensor represent the 69°, 49°, 29°, and 9° BTDC marks. It may take the PCM one engine revolution to determine crankshaft position.

Fig 1: Crankshaft Position Sensor

Courtesy of DAIMLERCHRYSLER CORP.

1 - CRANKSHAFT POSITION SENSOR

Fig 2: Timing Slots

Courtesy of DAIMLERCHRYSLER CORP.

1 - TORQUE CONVERTER DRIVE PLATE

2 - SLOTS

The PCM uses crankshaft position reference to determine injector sequence, ignition timing and the presence of misfire. Once the PCM determines crankshaft position, it begins energizing the injectors in sequence.