Want some info on crank re learn
Want some info on crank re learn I was on here a couple days ago and i read what the crank relearn did and why it was important. It also talked about how it read the difference in pulses between the cam and crank sensor. I can't seem to find the post now and would like to read through it again. Also i was wondering even if you didn't throw the re-learn code if it could hender the performance of the engine. For example could it cause the engine to hit a rev limiter bellow what it should or anything like that. Any info on this subject would be appreciated. I did a search and read through it, but all i found is how to do the re learn not information about the technical aspect of it or the original post i read.
On The Tree
Joined: May 2005
Posts: 132
Likes: 0
From: North Carolina
The PCM uses Crank Position pulses for fuel and ignition timing as well as misfire diagnostics. There are always slight "variations" in crank pulses so we have to do the relearn so the computer can learn what variations are normal. Anytime we change a crank sensor, crank, engine, PCM or otherwise change the relationship between the crank sensor and crank trigger (reluctor wheel), we need to do a relearn.
When it doesn't have the crank sensor stuff all
trimmed up it will run rougher (I saw this after
swapping PCMs, with the CKP relearn being inhibited
by a mystery EVAP system fault). Should not affect
things like rev limiter though perhaps a really messed
up crank sensor would do that, plus not learn. The
crank learn seems to be a really "fussy" process that
will refuse to get done, if you have certain other
codes set or prerequisites not met.
trimmed up it will run rougher (I saw this after
swapping PCMs, with the CKP relearn being inhibited
by a mystery EVAP system fault). Should not affect
things like rev limiter though perhaps a really messed
up crank sensor would do that, plus not learn. The
crank learn seems to be a really "fussy" process that
will refuse to get done, if you have certain other
codes set or prerequisites not met.
