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This indicates there is an open circuit from the PNP switch ( park neutral position).
This could be a voltage issue from the ignition switch, or a failed PNP switch on the side of the transmission.
Try working the transmission shift lever back and forth through the gears to see if it will jar the switch enough to get it to start reading again.
Do the lights come on on the dash when the key is turned to run?? ( ses , brake, glow lugs, etc)
Ok well then the PNP switch has failed, and need to be replaced.
Here is a bulletin on this condition, you described exactly.
Some customers may comment on one or more of the following conditions.
Moisture contamination within the Park Neutral Position (PNP) Switch may cause this condition. This is sometimes referred to as the Neutral Start Back-up (NSBU) Switch. On a left turn, water spray from the left front tire is directed directly at this switch. Proper installation of the "Front Shield" and "Rear Shield" are essential for proper repairs.
A blank PRNDL display may indicate a condition with the PNP switch and/or one or more of the four signal circuits from the PNP to the TCM.
Or, a blank PRNDL display may also occur if an out of line condition exists with the Serial Data Circuit (CKT 2470, yellow wire) from the TCM to Splice Pack 205.
If the Gear Selected display does not match the shifter position in the vehicle, diagnose using one of the following methods.
The PNP switch, as referenced in SI, is known as the NSBU switch in the Parts information. It is now serviced with a Park Neutral Position Switch Kit, P/N 29540479.
Important: If the old PNP switch will not slide from the selector shaft without the effort, the selector shaft may need to be filed to remove flaring on the end of the selector shaft. This is important, installing the new switch onto a selector shaft that has damage will cause damage to the new PNP switch.
Important: If the new PNP switch will not slide onto the selector shaft easily, the selector shaft may need to be filed to remove flaring on the end of the selector shaft. This is important, installing the new switch onto a selector shaft that has damage will cause damage to the new PNP switch.
Tighten Tighten the bolts to 27 N·m (20 lb ft).
Important: Installation of the front shield and rear shields are important. Without proper installation of the shield, a return repair is probable. Follow all directions as listed on the installation instructions sheet included in the Switch kit, P/N 29540479.
Tighten. Tighten the nut to 24 N·m (18 lb ft).
Switch kit, Park Neutral Position