RAM 2500 Truck 2WD L6-5.9L DSL Turbo VIN 6 (1998)
Engine Speed Sensor: Description and Operation
CRANKSHAFT POSITION SENSOR (CKP)-ECM INPUT
Crankshaft Position Sensor (CKP) Location
The Crankshaft Position Sensor (CKP) is located on the lower left-rear side of the engine behind the starter motor.
Engine speed and crankshaft position are provided through the CKP. The sensor generates pulses that are the input sent to the Engine Control
Module (ECM). The ECM interprets the sensor input to determine the crankshaft position. The ECM then uses this position, along with other
inputs, to determine injector firing sequence and fuel timing. The sensor must be powered up by 5 volts to operate.
The sensor is a hall effect device combined with an internal magnet. It is also sensitive to steel within a certain distance from it.
Crankshaft Tone Wheel
The engine crankshaft is equipped with a bolt-on tone wheel. The tone wheel is equipped with 35 teeth and a gap where the 36th tooth should be
placed. This missing tooth indicates to the ECM the relative position of cylinder #1 to the Top Dead Center (TDC) position. This does not mean
that cylinder #1 is at TDC. When the CKP is aligned with the missing tooth, the missing tooth is 60 degrees away from cylinder #1 TDC position.
The teeth cause pulses to be generated when they pass under the sensor. The pulses are the input to the ECM.
