Key Fob won’t open if used to start engine.

[JPtru]

2006 Ram 2500 Diesel- So I have narrowed down my weird issue regarding my key fob. I always need two keys on my key chain. Both keys can always start my truck, however the key that was last used to start the engine will not operate the remote door locking/unlocking. Until I use the other key to start the engine, at which point the door lock ability switches to the other key. What on earth could be causing that?

 

[JD Dotson]

Did you ever figure the issue out? I am currently having the exact same issue. Started a month ago. Been chasing electrical gremlins for a while. New tipm installed today no fix to the locking issue. All New ignition parts in the column i did last year. Was working until i removed an aftermarket remote start that was failing then a day later noticed no lock unlock. Had to get a new key fob, i only had one key with remote, once i programmed it i noticed the one key worked to lock unlock. But the new one didn’t. So playing around my issue is the same as you described. Funny thing is the drivers door lock button is acting weird along with this issue.

 

[MrBonez]

Did you ever figure the issue out? I am currently having the exact same issue. Started a month ago. Been chasing electrical gremlins for a while. New tipm installed today no fix to the locking issue. All New ignition parts in the column i did last year. Was working until i removed an aftermarket remote start that was failing then a day later noticed no lock unlock. Had to get a new key fob, i only had one key with remote, once i programmed it i noticed the one key worked to lock unlock. But the new one didn’t. So playing around my issue is the same as you described.

Funny thing is the drivers door lock button is acting weird along with this issue.

That may be the root cause of your issue.
If it's acting up with a manual lock/unlock of the door by it's button, whatever issue it may have in the door could also be what's keeping it from actuating the lock solenoid via your remote.

You haven't said (Yet) if pressing the remore buttom twice to fully (All doors) unlock the truck is acting any different or not with the remote.

Since you've described it as being only for unlocking it with the remote to get in yourself AND that same door seems to have an operational issue with it's manual lock button, that narrows it down to a possible problem in the door itself, not the remote.

Check that and go from there.