The Electrohydraulic Control Unit Assembly of the NAG1 transmission contains a temperature sensor
to monitor the transmission oil temperature. This sensor is wired in series with the transmission
Park/Neutral switch. The Transmission Control Module (TCM) expects to see a valid voltage level
from the sensor when the shifter is in Reverse or any forward Drive position. The TCM also expects
to see an open circuit condition when the shifter is in the Park or Neutral position. When the controller
detects an open circuit when in Reverse or any forward drive position the DTC will set. Note: Due to
an open circuit condition in Park or Neutral, the TCM substitutes the Transmission Temperature
reading with Engine Temperature when in Park or Neutral.