Freelander System Description and Operation
ENGINE MANAGEMENT SYSTEM - SIEMENS
18-4-18 DESCRIPTION AND OPERATION
CKP Sensor
The CKP sensor provides the ECM with a digital signal of the rotational speed and angular position of the crankshaft,
for use in ignition timing, fuel injection timing and fuel injection quantity calculations. To determine the exact position
of the crankshaft in the engine cycle, the ECM must also use the input from the CMP sensor.
The CKP sensor is mounted on the front of the gearbox housing, in line with the outer circumference of the torque
converter. The sensing tip of the CKP sensor is adjacent to a reluctor ring formed in the periphery of the torque
converter. The reluctor ring has 58 teeth spaced at 6
°
intervals. A gap equivalent to two missing teeth, 36
°
After Top
Dead Centre (ATDC) of No. 1 cylinder, provides the ECM with a reference point.
The CKP sensor operates using the Hall effect principle. A permanent magnet inside the sensor applies a magnetic
flux to a semiconductor, which receives a power supply from the main relay. The output voltage from the
semiconductor is fed to the ECM. As the gaps between the poles of the reluctor ring pass the sensor tip the magnetic
flux is interrupted, causing a fluctuation of the output voltage and producing a digital signal.
If the CKP sensor fails the ECM immediately stops the engine.
