Learning Cycle

[AllThumbs]

I have seen several references to a learning cycle but a search did not turn up much.

When does the PCM do a learning cycle? If I replace the PMD does the PCM do a learning cycle on its own or is a tool needed? How about a new chip? When do you need to do new timing?

Anyway, kind of confused on this issue. Any clarification would be appreciated.

:confused:

[DmaxMaverick]

It's a non-issue with the PMD. The PMD is a dumb device, and theoretically, they should all be the same with no variation in performance. It works or it doesn't, essentially. The "learn" you may be referring to is the calibration resistor, and that happens at 20-50 start and/or warm-up cycles. As long as there is a functioning resistor in place (in the PMD connector socket) and it's value is not out of the PCM's ability to calibrate the pump within spec, it's a silent process. The resistor value is read and stored until the next read cycle. If you were to remove it completely, it may be days/weeks/months before the PCM misses it, depending on several conditions.

[AllThumbs]

OK, that is good. It means I don't have to do anything.

[JohnC]

If you change the resistor and you want the PCM to recognize it, you have to do the "learn" thing. Also, if you change the relationship between the crank sensor, crank and timing cover, change the PCM or change the pump, you should re-learn the TDC offset (same process).

Lastly, the 6.5 PCM learns how to balance the injectors for a smooth idle. (IIRC)

[AllThumbs]

OK, I think we are getting down to what I wanted to know. How do I re-learn this process? Do I need to take it someplace, let it do it itself, ????

[JohnC]

If you have a Tech II or similar scanner, it's easy.

What are you trying to accomplish? If all you replaced was the PMD, it is not necessary.

[AllThumbs]

I am replacing the PMD. I do not know what resistor is in the old one and will not likely remove the old one since it is not worth it. Since it probably has a #5 in it, that is what I will put in the new one.

[AllThumbs]

John, I am replacing the PMD and also installing a Kennedy chip set for towing. Will that require a "learning cycle"? Will it start to get it to my local guy who I know can do that?

Thanks much.

[racer55]

John, I am replacing the PMD and also installing a Kennedy chip set for towing. Will that require a "learning cycle"? Will it start to get it to my local guy who I know can do that?

Thanks much.
Replacing the PMD alone will not require the relearn,but re-chipping or replacing the ECM will need the relearn to be done.The new chip will need to know the parameters the engine is running at or intended to run at.
TDCO relearn is the one that requires attention.

[JohnC]

Replacing the "chip set" requires replacing the PCM in a '96, so, yes, you should do a relearn. It will run, however, without. In fact, it may do the relearn automatically, depending on the state of the logic circuits when you get it.

[AllThumbs]

Well, thanks folks. It is in the mail so we will know soon.