Crank relearn and cam retard offset question

[EJ_74]

Working on my 2000 C2500 5.7 (now 383). Ordered a tuned PCM and installed it today. It runs, no check engine light, but I understand doing a crankshaft position relearn is recommended.

I set the distributor offset to 0 (+/- 2) degrees @ 1000 rpm on the old PCM. Do I need to readjust this for the new PCM? And after performing a crank/CASE relearn, will this change the offset?

My scan tool can't do the relearn so I plan to take it to a shop tomorrow. But was wondering if these adjustments affect each other. If I would need to change the distributor setting before/after the crank procedure

 

[Vikingdude]

I'm not 100%, but I think setting the CMP retard is a function of timing, crank sensor, and cam sensor. If none of those things has changed, I would assume its still ok. Dash command is an ok app to have on hand. With a cheap amazon Bluetooth OBD2 you can check CMP retard at home.

 

[EJ_74]

I can read the CMP with my scan tool, it just can't do crank relearn. I guess I will get that done first and then check CMP when I get home just to be sure

 

[BeXtreme]

I can read the CMP with my scan tool, it just can't do crank relearn. I guess I will get that done first and then check CMP when I get home just to be sure

Just make sure your CMP is good. You shouldn't need to run another one if you don't have a check engine light on. There is a procedure in this thread that supposedly will let your truck do the crank relearn on it's own.

https://www.gmt400.com/threads/case-learn-or-crank-relearn.6423/

 

[EJ_74]

I was able to borrow a scan tool from a shop and did the crank variation learn. Checked the CMP and still within spec. Engine is spark knocking a lot though when put under load. Wasn't doing that before the computer swap and I haven't messed with anything else. Guess I'm going to get in touch with the people who tuned it

 

[Tom400CFI]

I'd pursue the tune, too. IDK how or why you'd need to do a Crank relearn. The crank sensor says, "Now, now, now, now, now..." and that's it. It's mechanically keyed to the crank in one, fixed position that TELLS the ECM where the crank is. I don't think I'd want to be "relearning" the ECM what the crank signal is; it should be TDC for 1/6, 8/5, 4/7, 3/2...and should stay that way for the life of the engine.

 

[EJ_74]

I'd pursue the tune, too. IDK how or why you'd need to do a Crank relearn. The crank sensor says, "Now, now, now, now, now..." and that's it. It's mechanically keyed to the crank in one, fixed position that TELLS the ECM where the crank is. I don't think I'd want to be "relearning" the ECM what the crank signal is; it should be TDC for 1/6, 8/5, 4/7, 3/2...and should stay that way for the life of the engine.

Yes absolutely. I don't think the crank signal just changed all of a sudden. When I got it tuned I also got a new computer. So I just wanted to calibrate it to get it used to my engine

 

[Tom400CFI]

I think driving it will accomplish that....inasmuch as a computer gets used to an an engine. :thumbsup: