Crank Relearn after PCM Changes
03-03-2006, 07:47 PM
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Crank Relearn after PCM Changes Well I just got my PCM back from Wait4MePermonance and I found a piece of paper inside the box that said a Crank Position Relearn is needed after the install. I have searched this site and I am still not sure what exactly I need to do now.
Has anyone done this? Can I do it without any tuning software? THANKS!!!
Has anyone done this? Can I do it without any tuning software? THANKS!!!
03-03-2006, 07:59 PM
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yep i have done this you need GM tech II or just take it to your local dealer tell them you need a crank variation relearn it should cost less then $25 and takes about 5 minutes max! man will you hate life if you dont do this though....
03-03-2006, 08:12 PM
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So I am guessing my car will run like crap if I don't get a crank position relearn with some sort of bi=directional scanner? Is it safe to drive to the dealer? Is the dealer the best place to get a crank position relearn done? Thanks.
03-04-2006, 08:12 AM
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Well I just called the Chevy dealer and was quoted $85 for a crank position relearn
So I guess I will need to just bite the bullet and pay them to have it done. If anyone has any other ideas please let me know. Thanks.
So I guess I will need to just bite the bullet and pay them to have it done. If anyone has any other ideas please let me know. Thanks.
03-04-2006, 08:15 AM
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I should also mention that I thought I read somewhere that the PCM would do a crank position relearn by itself after driving the car for about 100 miles. Is this true???
03-04-2006, 08:53 AM
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The Crankshaft Position (CKP) sensor sends pulses to the PCM as the reluctor wheel teeth rotate past the CKP sensor. The PCM uses the CKP pulses to synchronize the ignition and fuel injector operation, and to time the interval between each CKP pulse. The PCM determines when an excessive change in crankshaft speed occurs by comparing each new time interval with the previous interval. A misfire causes an unexpected change in the crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if the crankshaft speed changes more than an expected amount, the PCM interprets this as a misfire. The interval between CKP sensor pulses is extremely small. At high engine speeds, slight variations in the following components make misfire detection difficult:
Crankshaft
Reluctor wheel
CKP sensor
The PCM learns variations during the Crankshaft Position System Variation Learning Procedure. The PCM compensates for these variations when performing detect misfire calculations. Only a scan tool can command the PCM to perform the Crankshaft Position System Variation Learning Procedure again.
Perform the learning procedure after the following actions:
A PCM replacement
Any operation or repair involving the crankshaft, the CKP sensor, or the CKP sensor to reluctor wheel gap relationship.
An engine replacement.
The ignition switch is in the ON position until the battery is drained.
FWIW, this is lifted directly from the GM service manual. I was under the impression that EFILive could do a CASE relearn as well? Hopefully someone familiar with Live can chime in and verify.
Crankshaft
Reluctor wheel
CKP sensor
The PCM learns variations during the Crankshaft Position System Variation Learning Procedure. The PCM compensates for these variations when performing detect misfire calculations. Only a scan tool can command the PCM to perform the Crankshaft Position System Variation Learning Procedure again.
Perform the learning procedure after the following actions:
A PCM replacement
Any operation or repair involving the crankshaft, the CKP sensor, or the CKP sensor to reluctor wheel gap relationship.
An engine replacement.
The ignition switch is in the ON position until the battery is drained.
FWIW, this is lifted directly from the GM service manual. I was under the impression that EFILive could do a CASE relearn as well? Hopefully someone familiar with Live can chime in and verify.
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03-04-2006, 10:53 AM
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Another alternative is the "Auto Lab" type franchises. I have friends who paid $30-50 for the service. About 1/2 the cost of the dealer. Also,in addition to the HPTuners and EFLive, any other of the scan only software with bi-directional cables can perform the CASE Learn.
03-04-2006, 01:46 PM
#11
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you *may* not even need to do the relearn... probably will... but if it's required it should set an SES light for it
ace, you only need to do a crank relearn in 2 situations:
1. NVRAM is cleared
2. You put a new PCM in the car
and even then you may not have to do a relearn...
I used to swap PCMs between 2 different ones often, never had to do a relearn... however fast forward to end of last year... I swapped the same PCMs and this time I did have to do a relearn (set an SES to do it, hard to start, etc...)
ace, you only need to do a crank relearn in 2 situations:
1. NVRAM is cleared
2. You put a new PCM in the car
and even then you may not have to do a relearn...
I used to swap PCMs between 2 different ones often, never had to do a relearn... however fast forward to end of last year... I swapped the same PCMs and this time I did have to do a relearn (set an SES to do it, hard to start, etc...)
03-04-2006, 01:48 PM
#12
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Arctic,
Does your car drive...?
If it does, then you could probably get by without until you run into sonmeone who has EFILive/HPTuners or some scan tool that can do a Crank Position Variation relearn.
As quoted by Dave_62 above, the PCM uses the Crank Position Variation relearn for "calibrating" its misfire detection algorithm; engine should still be able to run fine.
Does your car drive...?
If it does, then you could probably get by without until you run into sonmeone who has EFILive/HPTuners or some scan tool that can do a Crank Position Variation relearn.
As quoted by Dave_62 above, the PCM uses the Crank Position Variation relearn for "calibrating" its misfire detection algorithm; engine should still be able to run fine.
03-04-2006, 03:15 PM
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ace, you only need to do a crank relearn in 2 situations:
1. NVRAM is cleared
2. You put a new PCM in the car
1. NVRAM is cleared
2. You put a new PCM in the car
03-04-2006, 04:24 PM
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Actually I installed the PCM back in my car today and it seems to be running GREAT!!! I am guessing that I do not actually need to do a crank relearn because it is my original PCM. I thought that I needed to do a relearn because the paperwork I was sent back with my PCM mentioned doing a crank relearn. I am thinking that maybe the crank relearn is only needed if I was using a new PCM and if I was sending mine in as a core. So thanks for all of the feedback. It really did help. I think that mail order tune I got only changed the REV LIMITER, SHIFT POINTS etc. AND SO A RELEARN IS NOT NEEDED FOR THOSE CHANGES WITH THE ORIGINAL PCM. Just my guess though. I hope it doesn't start running like crap down the road. Thanks again
03-06-2006, 10:59 AM
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Originally Posted by joecar
Arctic,
Does your car drive...?
If it does, then you could probably get by without until you run into sonmeone who has EFILive/HPTuners or some scan tool that can do a Crank Position Variation relearn.
As quoted by Dave_62 above, the PCM uses the Crank Position Variation relearn for "calibrating" its misfire detection algorithm; engine should still be able to run fine.
Does your car drive...?
If it does, then you could probably get by without until you run into sonmeone who has EFILive/HPTuners or some scan tool that can do a Crank Position Variation relearn.
As quoted by Dave_62 above, the PCM uses the Crank Position Variation relearn for "calibrating" its misfire detection algorithm; engine should still be able to run fine.
I was throwing the CPS relearn MIL code and tried multiple trips to 3 different dealers and their teams of monkeys trying to get it to successfully relearn (this was back in 00 when there wasn't DIY software available). Turned out to be a POS PCM core from Ed Wright/Fastchip - bought a new stock PCM core and had it flashed with my stock tune/OS at the dealer - ba-da-bing, no more problems getting the relearn done on the new PCM. Too bad I had to be the one to eventually figure it out.
Rob (Bad30th)
Last edited by Bad30th; 05-20-2011 at 03:41 PM.
11-16-2007, 04:49 PM
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Crank position relearn I just started my engine today and I got the same piece of paper from wait4me. Have you found out anything else? My engine/trans runs fine. It is a 2004 vortec in a 58 pickup. Thanks Mark
11-20-2007, 01:50 PM
#18
this was an old thread, but since you bumped it, id like to ask about this. I just put a 98 motor in my 00 camaro. Installd a cam etc while it was out. Do I need to do this? I havent gotten it tuned yet, but it wont idle and runs like crap.
