Ok, so I guess the P/N Switch is also the Neutral Safety switch.
"Regarding the P/N switch:
Some wiring harnesses ground the Park/Neutral wire so that the ECM always thinks the vehicle is in Neutral or Park. The reason is to prevent the SES (service engine soon) or Check engine light from being turned on due to lack of a VSS signal. The service manual states: The ECM uses the P/N signal as one of the inputs to control: Idle Air control; VSS diagnostics; EGR. If the P/N wire is grounded in drive, the EGR would be inoperative , resulting in possible detonation.
Without the P/N switch connected (grounded) the engine will run ok but engine speed may drop excessively when shifting into gear. "
I just looked at the Purple wire on the new harness, it has a tag on it which reads: Grounded when in Park and Neutral. Which would explain why when I data logged the motor, it showed that the vehicle was in "Drive" the entire time.
it's no trouble to wire it up., but I'm just curious..... if the ecu doesn't get a grounded signal when in Park / Neutral how does it effect the running of the motor?
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