2005 4x LE 95k, My Service Engine Soon light came on and I took it to an auto parts store to have them check the code for me and the Park Neutral Position Switch came up. From what i've researched I shouldn't be able to drive the truck anymore so I figured I'd run the order of events past you guys to see if anything stands out.

Order of events:

1. Noticed Trans not shifting properly between 30-60 mph and sometimes not catching when moving lever between P & D. Had the trans flushed and new fluid, no signs of leaking with the Rad. Ran fine, Issue gone.

2. Week later trans acting up again. Took to same Trans shop, added a friction modifier and said it was the torque converter. Ran fine, Issue gone.

3. 4 days later on a normal commute, Cruise Control won't engage, light comes on but not holding speed.

4. 2 days later, left for 650 mile road trip(w/no cruise control) and after about 300 miles "Service Engine Soon" comes on. Re-read the manual and checked all possibilities and continued on my way so that I could get to a shop at my destination.

5. Arrive in town, hit an auto parts store to check for codes and got a "Park Neutral Position Switch" code. Researched and found squat! After truck cooled, check the inside of the rad cap and find that white stuff that shouldn't be there. Took the truck to a shop and had to replace the Radiator. Picked up the truck, light was off, trans ran great, no overheating, good as new and luckily not a transmission rebuild. Ran fine, no issues.

6. 5 days later, head back home (650 miles) and half way the "service" light comes back on. Checked the rad cap, nothing, shifting fine the whole way home, no idea what is wrong.


From what I've been finding there are all sorts of relay's and switch's either in or around the transmission housing. Could the "Park Neutral Position Switch" code be because of the rad/tran issue and just throwing out a bad code? Also could any of this affect my Cruise Control?

TIA