2002 Silverado 2500hd crankshaft variation relearn

Brett Technician New York Posted   Latest  
Unsolved
Driveability
2002 Chevrolet Silverado 2500 6.0L (U LQ4 Bi-Fuel) 4-spd (4L80-E) — 1GCGK29U92Z280638
P0300 — Random/Multiple Cylinder Misfire Detected
MIL Flashing

Hey everybody-

Have this 02' 2500HD that's giving me a hard time running the crankshaft variation relearn. Runs fine. Customer did his own plugs and wires. Has roughly 210k on it. MIL flashes on highway only. I have run this test many times on these trucks. Never an issue. Go through the proper procedures..parking brake on.. coolant temp over 160 etc. As soon as I whack the throttle scan tool says “test in progress” and never goes any further. I disconnected battery. Tried both snap-on and Autel scanners. Both behave the same way. Looking at TPS- I can only get 99% out of it. Does it need 100% to run? I plugged in another TPS that we had kicking around and same thing- 99%. Any thoughts much appreciated!

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Caleb Diagnostician
Indiana
Caleb
 

I would put a scope on the CKP and CMP. With 210k and being in NY there's a good chance the CKP is rust jacking. Post a scope shot of these circuits when the truck acts up.

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Danny Technician
Wisconsin
Danny
 

Find someone with a tech2 and try that. I tried and failed with an autel and the tech 2 did it.

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Glenn Owner/Technician
Texas
Glenn
 

Hi Brett, If you have a P0300 setting, it will not perform the relearn. You will need to determine why it has that code and resolve that issue first. A flashing MIL typically means pending CAT damage due to excess fuel or an overly lean mixture.

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Brett Technician
New York
Brett
 

I have scoped the crank signal while trying to do the test- and nothing looks abnormal. She is crusty/rusty for sure. Brake signal has been confirmed. It has never illuminated the check engine light after the event. Just a stored P0300 on occasion. It runs great for being run hard and put away wet. And salty. I have rectified this issue many times with a relearn- but this one has me riding the…

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Rusty Owner/Technician
Massachusetts
Rusty
 

It was fairly common to find those trucks with “phantom” P0300 codes that could be resolved with a CKP relearn. I think that’s what he’s trying to do.

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Rogelio Owner/Technician
Texas
Rogelio
 

I've had some where it does need to be the tech 2. Even the emulator has worked for me when scanners haven't. But also make sure your brake pedal signal is registering properly, or it won't completely go into learn mode.

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Joel Diagnostician
California
Joel
 

I had one silverado I could never completed the ckp relearn no matter what scanner I used , a friend did it with tech 2 in seconds

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Agree
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Saul Diagnostician
Texas
Saul
 

Same thing happened to me.

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Brandon Diagnostician
Arizona
Brandon
 

If it has a rev limit, ive run into not letting go of the throttle soon enough and failing the relearn.

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Manuel Diagnostician
New Jersey
Manuel
 

Relearn will never go if p0300 is setting

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Robert Technician
Michigan
Robert
   

Timing chain sounds stretched to me ; PCM needs to know this random eliminated & if it is ; A crank relearn must be done before P0300 diagnostics.

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Dan Owner/Technician
Texas
Dan
   

… “Customer installed parts” … really make me wonder if he fell for the old Bosch Platinum brand (shitty and cheap) from “The Zone”… or … The proper AC Delco Iridium Plugs (way more expensive and proper for the application)… Did you look to see what he put in it ? … Dan .

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Timothy Owner/Technician
Wisconsin
Timothy
 

If it is counting misfires at the time of the learn, it will never complete. I've yet to have an issue, but I've been using a Tech 2 for decades for this, and have never attempted it with an AM tool… OTOH, anything with a crank that is too far out of range will never complete either.

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James Owner/Technician
Massachusetts
James
 

Last year I had a 2500 with the 6.0 at my shop for the same issue. Engine light flashed on the highway only. I was able to perform the relearn with my scanner but it did not fix the issue. I ended up finding the intake gaskets leaking a little. Replaced them and the problem went away.

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Israel Technician
Florida
Israel
 

Sounds like you need a tech2, good luck

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Adam Owner
Arizona
Adam
 

I ran into this before and posted about it before, but it was a 8.1L. For some reason the aftermarket tools require V8's 4000 RPM to enable relearn. Some neutral/park ECM programs do not allow the test to reach that RPM on WOT, so it will not complete the test. I, as the others pointed out, found only the Tech2 to accomplish the relearn. Neither Autel nor Launch seemed to care, as neither…

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Brett Technician
New York
Brett
 

Thanks for all the suggestions everybody. Truck left last night as it was needed for salting duty. It should be back end of the week and I will update things once I get back into it. Plugs and wires are all AC delco. Misfire counters don't count up at all prior to running the test.

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Matthew Owner/Technician
Massachusetts
Matthew
 

i have run into this a couple of times. remove the crank sensor and clean rust from mounting surface. I struggled the first time and this happened to me. I hope this helps

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Brett Technician
New York
Brett
 

Ok- truck came back. To all of you whom suggested rust- you are todays winner. I wasn't able to be scientific about this because I spent about 30 minutes trying to gently remove the crank sensor and then gentle turned into less gentle and I think we all know how this ended. So- I can't say if it was rust or the sensor- but the amount of rust stuck to the sensor even after my abuse was pretty…

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Glenn Owner/Technician
Texas
Glenn
 

Hi Brett, Even down here in South TX that happens. I had one last year that I thought I was going to have to drill and break it out in pieces. Apparently, the engineers don't plan beyond initial testing on a track. The real world has different effects. Glad you got it figured out.

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Brandon Diagnostician
Arizona
Brandon
 

Same here in AZ but I had to drill it out.

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Glenn Owner/Technician
Texas
Glenn
 

The best rust solvent I have used for years is 3 parts tranny fluid and 1 part Acetone. That combination works well in a pressurized steel canister sprayer. I learned that year ago working on rusty restorations.

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Brett Technician
New York
Brett
 

We all have our “rust certifications”!

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