Is the CKP Relearn a "must do"?

[PerfectCreature]

I bought a mail order tune quite some time ago, and it has been sitting in my closet.
I was reading the instructions online and aside from the security relearn, there is a mention of a CKP Variation relearn procedure and I do not have a Tech II or Snap-On tool that could do what it needs done.
The security relearn does not worry me, but the CKP does.
I am wondering if it is a thing I have to have done, and what the effects of not having it done will be.
I tried looking it up but did not find much information on it, other then I may need it and I may not. Is there any way I could tell if I need it?
Its my understanding that is used to detect misfires, and that is all.
The PCM is not the one that came stock, it is from another car.
My stock one is still in the car, and I used one I received from the junk-yard as the core to be programmed.
I had intentions of putting it in a few days ago, bit got discouraged after I read out the procedure.
Looking for any advice or help.
Thanks,

[mfuller]

The relearn allows for the PCM to accuratley control spark timing.
You should do this whenever you replace/reprogram the PCM or replace the harmonic balancer (it has a 24x tone ring pressed in the backside for low-rpm spark timing).
If your car throws a code with the new PCM, then you need to get the re-learn done.

[PerfectCreature]

The relearn allows for the PCM to accuratley control spark timing.
You should do this whenever you replace/reprogram the PCM or replace the harmonic balancer (it has a 24x tone ring pressed in the backside for low-rpm spark timing).
If your car throws a code with the new PCM, then you need to get the re-learn done.

So then there is a possibility it won't toss a code? What should I be looking for...just an SES or Check Engine light or something?
I don't actually own a code reader as I have had no need to go out and buy one.
I called around and the only place that can do this so far is the dealer, I do not want to risk my tuned PCM being flashed to stock....
I still have a few shops left before my hunt is over.

[mfuller]

It is possible that it won't throw a code.
You'll know for sure if you get a Service Engine Soon light.
You can go to any AutoZone or Advance Auto, etc. and they can read the trouble code for you (usually for free).

[PerfectCreature]

Okay, I have the box in my closet, I will have to put it in and find out.
Does it matter if the service codes match?
What is the likelihood I would not need the relearn?
I will call the last few shops and see what they say.

[TGP37]

I replaced my crank sensors, balancer, pcm and turned the key. She runs and runs great, no ckp relearn for me. The PCM will eventually figure it out and relearn on it's own (from what I've been told).

Replacing it, you have a 1/24 chance of lining it up just right, lol.

I wouldn't worry about it.

[PerfectCreature]

Lining it up just right?
Do you mean the PCM?
I don't want to put in the tuned one if I have that small of a chance of getting it right.....

[pocket-rocket]

He means the chances of the engine stopping at the same location the engine that was hooked to the tuned PCM was the last time it was shut off, that way the 24x ring was in the same exact spot on both engines so the tuned PCM wouldn't throw a CKP code.

Say engine 1 (the one the tuned PCM came from was on the 4th tooth of the crank trigger wheel the last time it was shut down.

Then engine 2 (your cars engine) was shut down and it was at the 15th tooth.

With this scenario it's possible the tuned PCM would throw the code for CKP relearn. He says 1/24 chance because there are 24 teeth on the wheel.

[PerfectCreature]

Oh, gotcha. That makes a little more sense. Thanks for the clarity. I suppose then, eventually, it would get to a point where they would line up on both ends?

[pocket-rocket]

I'm not a tuner, so I can't say for sure. But I would imagine once out of sync, always out of sync... until a CKP relearn is done.