do i need a crank relearn?

[jake ss]

i recently had the computer on my truck unpluged to do some repair work(welding)and i was wondering if i need a crank relearn because it doesnt run as strong now,anybody have any idea? Its a 03 ECSB 5.3 w/full bolt ons and predetor tune

[VinceTrifecta]

Is the check engine light on and/or do you have P1336 code? If so, you need crank relearn.

If all that was done was the computer was unplugged, then crank relearn should not be necessary.

[Joe]

Is the check engine light on and/or do you have P1336 code? If so, you need crank relearn.

If all that was done was the computer was unplugged, then crank relearn should not be necessary.
I agree.
Just removing and re-installing the same PCM should not show any change in performance.

[HaulnA$$]

i recently had the computer on my truck unpluged to do some repair work(welding)and i was wondering if i need a crank relearn because it doesnt run as strong now,anybody have any idea? Its a 03 ECSB 5.3 w/full bolt ons and predetor tuneYou don't need a crank relearn but you do need a fuel/timing relearn. By unplugging the PCM you wiped out all the stored fuel trim data and adaptive timing data as well as the transmission adaptive shift data and now you must go through a few drive cycles for the PCM to relearn them. After about 100 miles, all should be back to where it was. HTH

[VinceTrifecta]

It is possible that the learned runtime information (LTFTs, idle, etc) were reset by disconnecting PCM and to that end it may need to "relearn", but I have heard the Gen III style PCMs store the learned runtime information in the EEPROM, which would not be cleared when the battery power is disconnected.

[jake ss]

thanks could changing the dampener/crank pulley do any thing to the engine timing? because i was reading somewhere else that anytime u mess with the dampener or flexplate ect. u should have a crank relearn done.

[VinceTrifecta]

Generally, it's when you mess with the CKP sensor that you need to worry about crank relearn.

But, I have heard that there are times when the engine will rev lazily and lose performance, but no P1336 code will be thrown, and a crank relearn is the fix. I have never personally run into this, though.

In theory, anything that changes the speed at which the engine revs up or down could trigger the need for a crank relearn.

I wrote an article about this, if you want to read it, it's here (http://www.trifectaperformance.com/tech/crankrelearn.htm). I'd say, drive it for 100 miles or so, just to be sure its not a learned runtime issue. If it feels "lazy" when it's revving after that, and performance is lost, a crank relearn would be worth a try but I'm hesitant to recommend it because I wouldn't want you to have to go spent $100 at the dealer for something that doesn't solve the problem.

Jake ss, I sent you a PM - I have a hand-held tool that could be used to do a crank relearn, if you want to try it.

[jake ss]

that is a great article vince!my battery did die with the key on once(POS ac delco battery)what would it take to try your handheld on my truck

[VinceTrifecta]

I need a few days to get the code working and tested (probably by Thursday), in the meantime you can drive it 100 miles or so. I'll shoot you a PM when I have something ready to test. Sound good?

[jake ss]

sounds good! thanks 4 all the help!

[DefEddie]

If you don't mess with the crank/cam correlation or remove the reluctor ring or crank sensor then you should not have to do a Crank relearn.
The crank reluctor spacing is saved in the computer,so the ecm can keep track of thing's like wear and stuff on the reluctor.
It's a mechanical part and wear's and move's and the sensor get's less sensitive etc... The ECM learn's this info and use's it to reference minute difference's and screen them out for a correct reading.
This isn't the best explanation,but should give you a good idea of what it is and why you would need to relearn it.
Taking the computer out mean's nothing,except that your fuel trim's will reset back to zero. As long as it's the same computer then you should have no crank relearn problem's.
Generally resetting the trim's will actually help performance. I once reset the trim's on a firehawk that was bracket racing,he broke out of his dial-in by 2 tenth's directly afterword's.