Strange transmission or PCM issue (need help)

[DatGuy1984]

Hi JK Gurus~

A little information about the vehicle first. 2008 Jeep Wrangler 2 door, Automatic Transmission, 4WD. Transmission took a dump and had to be replaced. Put in a used transmission from a 2010 wrangler 2 dr. Completed install and did the relearn parameters. Test drove vehicle around block and all was well. Brought the vehicle home and gave it a quick bath. Exterior only, no engine bay washing took place. Went to start vehicle a couple of hours later and the instrument cluster indicated PRNDL in Reverse!?!? Transmission will shift into each gear smoothly both from inside the vehicle and from under the vehicle. While shifting the indicator will go into R, D, and L 1 and 2. The indicator will not go into P or N. This prevents me from being able to start the vehicle at all. I test Park/Neutral Switch and it tested good to OEM Specs. I disconnected Bulk head connector from trans and Removed Negative From battery to try and "reset" PCM - no Luck. I scanned for codes - NO CODES PRESENT. Im leaning toward PCM as the TCM is integrated into it. Has anyone ever seen this before? I've done my fair share of diagnosing vehicles but im at a loss right now.

 

[BLACKJKU]

Are the shift cable linkage ends good, no slop or broken? Have you tried disconnecting one end of the cable and manually putting the trans in gear while someone watches the dash to see if it reads each gear?

 

[DatGuy1984]

Are the shift cable linkage ends good, no slop or broken? Have you tried disconnecting one end of the cable and manually putting the trans in gear while someone watches the dash to see if it reads each gear?

Shift cable linkage ends are good. No slop at all. Yes, I have disconnected the Cable and manually shifted trans in gear with someone watching PRNDL on dash. Same thing happens. When trans manually shifted to park it shows R on dash, when shifted from park to reverse or neutral it still show R on dash Then when shifted into Drive it will show D on dash. It just skips over neutral whether i am upshifting to R or Downshifting to D.

 

[Barry]

Sounds like in internal problem inside the trans. Or, the sensor that makes the light work on the dash Is haywire or out of adjustment (If there even is an adjustment.) Just a thought, may be all wrong.

 

[Barry]

Also check any ground wire near wher the trans work was done. Since the advent of the OBD system came out a bad ground will make a jeep electrical system do real strange things. Also it wouldn't hurt to see if all the wire connectoers are plugged in tight.