neelskit said:
I started having a similar problem to the OP. Intermittently, the indicator on the dash will not show the shifter in P, N, or D. When this occurs, R, and 1-3 are displayed when shifted. The strange thing is, the truck will not start in D, as it shouldn't. Is the neutral safety switch separate from the indicator switch? Also when this occurs, the door locks do not lock and unlock when shifted out/in to P. I've also had an intermittent REP followed by no start issue that started happening at the same time. When the truck decides to re-start, all is fine. Maybe my TB doesn't like all this below 0 weather we've had this winter...
It appears to me there's two circuits in the park/neutral switch.
The first circuit directly relates to starting. There's a pink wire that runs to the PNP switch, that's the hot for this particular circuit. This circuit will only be closed in Park or Neutral, and the output exits through a light-green wire. Literally the only thing that uses this neutral-safety circuit is for starting, everything else like gear display and locks are run from the second circuit.
The second circuit - a gray, yellow, white, and black/white all run into the PNP switch. Each wire runs to a different switch inside the PNP switch case and I believe are actuated in different combinations to ascertain the current transmission selection, acting like a binary system. There's a black wire that exits the PNP, I believe it should be pin D on connector C2, this is the ground for these switches. The ground wire runs up to the underhood fuse block, then comes back out and grounds to the lower-left side of the engine.
My first guess would be to scope out the ground wire and all four colored wires in this second circuit and make sure it's all good and gravy, and the connectors too. It sounds to me like maybe one or more of the colored wires in this circuit may be damaged. If everything checks out, it may be time for a new PNP unless someone has a different idea. Make sure to check continuity and check the wires themselves as fully as you can. These wires terminate at various pins on the PCM, and the PCM transmits your current selection via the Class 2 Serial bus to the instrument cluster to display. If everything else is good and you've replaced the PNP and it's still doing this, you may have some sort of issue in the serial data lines.
