Shift to park error won’t start
As you can see in the starting system wiring diagram provided the ECM requires the Automatic Transmission Internal Mode Switch signal to energize the starter relay.
First thing to try of course are the less expensive things. So disconnect the negative battery terminal and leave it for about 15 minutes before reconnecting it. This should reset the computer. Then test to see if that cleared up the issue. As i have read on several forums, this has worked well for many.
You may also want to try and apply a little bit of pressure on the shifter as it may just need adjusted.
Now if it said “Not in Park” it would possible be a bad or bent micro switch in the shifter which is actuated by the shifter knob. This is usually accompanied by a beeping noise.
SUGGESTIONS from forums:
CWB states: There is a microswitch with a metal lever that is a little out of adjustment. Dealers will replace the whole shifter but it can be fixed by slightly bending that lever. Do a search on this forum for the shift to park fix. By the way, you can tell how close you are to NOT being able to temporarily fix this problem by holding the reverse lockout as you shift to park. While still holding the lockout – turn off car. You will get the shift to park error. Slowly let out on the lockout. The quicker the error cuts off = the further you are from a permanent problem. Yes you have to take the console apart to fix it.
Brasknockles states: It is ok to disconnect and connect both battery cables together. It is a good and safe method to fully drain the pcm of voltage and reset the computer. You will usually have to let it idle so the vehicle can go through some relearn process. IT IS OK TO CONNECT BOTH BATTERY CABLES TOGETHER TO FULLY DRAIN THE PCM AND IT WILL DO A RESET.
2005 Cadillac STS starting wiring diagram
