Is a CASE Relearn really needed?
 

I installed a new PCM today (Overkill) and it was pretty much just plug-n-play. I didn't have to do the security relearn or the CASE relearn procedure. I drove it around and it drives more than fine. Why exactly would I need to do a CASE relearn? Would it make the car drive even better? I found a few auto-shops who said they can do it, but i don't want to spend any money if it really isn't needed. Any help would be appreciated. Also, the tune is fantastic (Thanks Will)!

I don't know the answers, but want to follow this thread, as am interested in tuning options
I'm sure someone on here has knowledge about this

My experiences with re-tuned PCMs are this:
- I have not had to perform a CASE relearn yet for anything.
- If you are using the PCM that came from your car and no security re-learn is required (it's still stored and good in the PCM).
- If you use a donor PCM (came from another car), then yes, a relearn is required.

Good question.

According to the factory service manual a CASE variation re-learn (AKA- Crank Position Variation re-learn) is necessary after replacing the engine, PCM or crank position sensor.
It doesn't say so, but I believe it's only necessary if DTC like P0300, P1336, P0315, or P0336 sets.
The purpose is to "synchronize' the timing of the crank position sensor with the PCM and establish the fuel cut-off point. I really don't know what the password relearn has to do with it since that can be worked around with a security re-learn procedure or programming with a Tech 2.
I have a Tech 2 and just for fun tried it to see what would happen. Simple process....just plug in, select CKP relearn in "Special Functions", put your foot on the brake and step on the gas pedal to WOT until the Tech 2 tells you to stop. As expected I didn't notice any difference. I would say if you don't have a code or a misfire it's not necessary.

Here's a video on the procedure:

I've never noticed any difference whenever I've done a CASE relearn after a PCM swap.