Trans temp sensor - P/N Switch circuit

WARNING: This page is about a different car, the 2006 Dodge Sprinter. However, it is still accessible from the selected car via links, so may be relevant.

The TCM will detect the selector lever in park and neutral positions. The TCM does this by monitoring the Transmission temperature sensor signal along with the shifter position signals. The P/N switch contact is operated by a cam located in the transmission which, opens a reed contact switch that is wired in series with the transmission temperature sensor. When the P/N contact switch is opened in park and neutral, the TCM senses a high transmission temperature. Confirming the P/N switch status. Note: In park or neutral, the TCM uses engine temperature (to avoid setting a DTC). The TCM sends a hardwired signal to the ECM that will allow the ECM controlled start circuit to engage in P or N only. The TCM also sends a P/N bus message to the ECM to confirm the P/N switch status.

The Normal Transmission Temperature Sensor resistance is between 500.0 and 2500.0 ohms. The normal voltage limits for the transmission temperature sensor, are between 0.5 and 3.0 volts.