Theory Of Operation
GENERAL OPERATION: The Powertrain Control Module (PCM) monitors the Gear Position Sensor Signals to determine which gear the Transmission is in. The Gear Position Sensor has a shared 5.0 volt supply, sensor ground and two position signals from the sensor. The signals to the PCM are in the form of a 5 volt square wave duty cycle. The Gear Shift Position Sensor quadrants are learned at the plant. These positions will need to be learned if a sensor or any Transmission Shifter components are replaced. The PCM monitors movement of the shifter along the X and Y axis to determine the shifter position. The X axis is left and right movement of the shifter which detects 4 different quadrants. The Y axis is forward and backward movement of the shifter which detects 3 different quadrants. The PCM uses the two duty cycle signals to make the determination of the shifter position. See the graph in the figure depicting the gear shifter positions and correlating duty cycles. DIAGNOSTICS: The normal operating duty cycle range for each signal is between 10% and 90%. If the PCM detects that the duty cycle for either signal is above or below the normal duty cycle range a circuit fault will set. The PCM also monitors the rationality of the shifter position by comparing the actual gear shift position feedback to the calculated gear shift position. The gear shift position calculation is based on the Transmission being in a forward gear with the Clutch Pedal not pressed, vehicle speed, engine speed, and calculated engine torque.