SRX AWD V8-4.6L VIN A (2004)
Camshaft Position Sensor: Description and Operation
CAMSHAFT POSITION (CMP) SENSOR
The CMP sensor is a hall IC type sensor. The sensor is true power on (TPO) at power up, which means it is capable of recognizing whether it is in front
of a tooth or a notch at power up, and to set its output accordingly. The sensor is a high technology product that integrates a self calibrating system that
compensates for environmental changes, such as temperature and air gap. The sensor is composed of a magneto-electronic module that generates a
magnetic signal and transforms it into a digital signal. The sensor operates in two functional modes. The first mode is the static functional mode. This
mode is valid at sensor power up. In this mode, the sensor behaves like a simple DC hall IC switch with two fixed switching points. The static functional
mode is active during the first 10 mechanical edges of the reluctor wheel and as long as the signal frequency is lower than 1.2 Hz, plus or minus 0.5 Hz,
with the one tooth reluctor wheel. When the signal frequency exceeds the previous mentioned limit, the sensor switches to the second functional mode,
the self-calibrating functional mode. This mode enables the sensor to reach high angular position accuracy, which is not possible to achieve in the static
functional mode. In the self-calibrating mode, the sensor acts as a field induction sensor, which is more accurate at higher engine RPM. The sensor
switches from self-calibrating mode to static functional mode when the signal frequency becomes lower than 0.3 Hz, plus or minus 0.1 Hz, with the
1-tooth reluctor wheel. When the sensor switches back from self-calibrating mode to the TPO mode, a pulse of short duration is generated on the sensor
output signal. The pulse may occur on the low signal state or on the high signal state.
The CMP sensor wiring consists of a 12-volt reference circuit, a low reference circuit, and a signal circuit. The CMP sensors work in conjunction with a
1-tooth reluctor wheel on the exhaust CMP actuators. The CMP sensors work in conjunction with an 8-tooth reluctor wheel on the intake CMP actuators.
As each tooth on the reluctor wheel passes the CMP sensor it sends a digital signal, which is an image of the wheel, to the ECM. The ECM processes this
information to determine the exact position of the camshafts, and to determine the optimum ignition and injection points of the engine.
CAMSHAFT RELUCTOR WHEELS
The camshaft reluctor wheel is part of the CMP actuator. This system consists of two different reluctor wheels. One for the exhaust camshafts on bank 1
and bank 2 and one for the intake camshafts on bank 1 and bank 2. The reluctor wheel on the exhaust CMP actuators has one tooth that extends 175
degrees around the circumference of the wheel. The reluctor wheel on the intake CMP actuators is an 8-tooth wheel that consists of four long and four
short high and low phases. The 8X reluctor wheel is also used for the limp home mode.
