B4000 2WD V6-4.0L OHV (1994)
Transmission Position Switch/Sensor: Description and Operation
Component (A/T)
PURPOSE
The Powertrain Control Module (PCM) uses the Park/Neutral Position Switch (input) to determine engine load and adjust engine operating
parameters according to PCM programming.
OPERATION
The PCM sends a 5 Volt reference voltage through PCM pin No.30 which travels to a terminal on the Park/Neutral Position Switch. Another
terminal of the Park/Neutral Position Switch connects to a common ground circuit that returns to to PCM pin No.46. With the transmission in the
park or neutral position the Park/Neutral Position Switch closes and allows current flow from PCM pin No.30 through the switch contacts and out
to PCM pin No.46.
This current flow results in a measurable voltage drop at PCM pin No.30 from 5 Volts to approximately 1 Volt or less.
The Park/Neutral Position Switch opens the circuit when the transmission is in any gear position other than park or neutral. The interuption of
current flow causes the voltage at PCM pin No.30 to return to 5 Volts.
The PCM monitors the voltage changes at pin No.30 and uses that information to determine transmission gear position.
