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Old 01-09-2019, 11:00 AM   #11
Hotwire
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Quote:
Originally Posted by 2kwik4u View Post
Is the DOD really that bad? It doesn't seem to bother me much on my '15 Sierra. I spend a good amount of time on the highway now, and am knocking back consistent 16-17mpg tanks without using the cruise at all (city expressway traffic). Taken a couple road trips with it and have seen 21mpg a few times. I've found I pick up about 1-1.5mpg by running premium fuel. Makes the cost per mile about the same between the two fuels, with it running noticeably smoother, spending more time in V4 mode, and not dropping to 5th on the expressway nearly as much. I suspect the added time in V4 mode, and the fewer kick downs to be the cause for the slightly higher mpg on 93. I haven't run before/after logs to see what the total timing is between the fuels, but I suspect I've picked up a degree or two.......anyway......that rambling is to say that I think the DOD on this truck is currently working like it's supposed to, and is there a way to prevent the lifter collapse issue that seems to be the only downfall to the setup? Stay on top of oil changes, and keep good oil in it? I hear of lots of people beyond you guys removing/disabling it, but I would kinda like to keep it unless there is something I'm missing?
He's already suffered a DOD lifter failure under warranty and was always wanting to find a work around. When I bought the Yukon it somewhat sealed the deal for him and wanted it gone because he didn't want to go through that work out of warranty. No way to prevent it, it's an engineering failure mechanism with no updated product to fix the issue, just replace and pray.

I kept it, the mpg difference, fuel cost, time at pump, etc is worth it for me.

Mike, your 2015 has some impressive tables for timing setting based on octane. I did not change any of the timing settings. If you do anything, I would get your truck tuned and lean out wide open throttle (Power Enrichment), made a significant amount of power difference.
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Quote:
Originally Posted by Teeleton
Hot wiring is bad news.
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Old 01-09-2019, 11:06 AM   #12
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Quote:
Originally Posted by ghettocruiser View Post
While this was sitting at the dealer I stopped in one night and poked around, they had the valve cover off and the number 6 rocker was loose. I thought this confirmed my suspicions of what was wrong, since this seems to be a common problem cylinder. After I started tearing into it, I noticed that the whole coil set was unplugged for the drive home. Now that I have the passenger cover off again, everything is back tight?? Could the shock of driving it unplugged have caused vibration to free the lifter? It seems very unlikely to me, but i dunno.

I'm going to pull the drivers side cover and see what I see next.

If nothing is loose and I unplug the AFM solenoid on the valley cover will this keep the DOD from activating long enough to put everything back together and test without fear of it collapsing again?

Ok, break over, back to work.
The vibrations from driving on 4 cylinders could have knocked it loose, but I don't have enough experience with them to say for certainty. Unfortunately you didn't have the opportunity to read the original codes beforehand to see if #6 was misfiring.

I don't know that I'd drive around w/ AFM disconnected, not that it would do harm, but think the ECM would put it into limp mode and you can't really troubleshoot that way? Hopefully Mitch can chime in, I haven't had a lot of time with the AFM, mostly avoided it up until the hybrid tahoe.
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Quote:
Originally Posted by Teeleton
Hot wiring is bad news.
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Old 01-09-2019, 11:36 AM   #13
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Let me test it, but I think if you put the truck in D instead of OD it won't go into AFM if you just want to test it. I will check at lunch if I drive or on the way home and report back.
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Quote:
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Hot wiring is bad news.
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Old 01-09-2019, 01:39 PM   #14
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Quote:
Originally Posted by Hotwire View Post
He's already suffered a DOD lifter failure under warranty and was always wanting to find a work around. When I bought the Yukon it somewhat sealed the deal for him and wanted it gone because he didn't want to go through that work out of warranty. No way to prevent it, it's an engineering failure mechanism with no updated product to fix the issue, just replace and pray.

I kept it, the mpg difference, fuel cost, time at pump, etc is worth it for me.

Mike, your 2015 has some impressive tables for timing setting based on octane. I did not change any of the timing settings. If you do anything, I would get your truck tuned and lean out wide open throttle (Power Enrichment), made a significant amount of power difference.
Thanks for the explanation. I think I'll keep the DOD myself.

I've been debating on a tune. I'm on the fence about modifying the tune myself (still have the HPTuners sitting around from the SS), or getting something that is a "semi-custom" like a black bear or similar. There are a few transmission settings I wouldn't mind changing, but overall like the way it shifts, and the power it has. Wouldn't mind it having an extra 10-15hp across the board to keep from downshifting on some of the larger hills we have on the expressways here.

Overall I'm really happy with the truck, and a bit leary of making any changes. I've got 26k miles on it from my driving, and it's not skipped a single beat yet.

Quote:
Originally Posted by Hotwire View Post
Let me test it, but I think if you put the truck in D instead of OD it won't go into AFM if you just want to test it. I will check at lunch if I drive or on the way home and report back.
I know if I put mine in M5 it won't go into AFM.
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Old 01-09-2019, 06:11 PM   #15
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Quote:
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I don't know that I'd drive around w/ AFM disconnected, not that it would do harm, but think the ECM would put it into limp mode and you can't really troubleshoot that way? Hopefully Mitch can chime in, I haven't had a lot of time with the AFM, mostly avoided it up until the hybrid tahoe.
I don't know for sure. The DTC description says whenever a deactivation solenoid circuit fault is set the ECM will return to V8 mode and shut off the injector to that cylinder, causing a misfire. On a side note I'm working on a gen 5 right now that has one AFM lifter that won't lock in DOD mode, you should hear the knock this thing makes in V4. Runs fine in V8 mode.
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Old 01-10-2019, 07:16 AM   #16
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Quote:
Originally Posted by ghettocruiser View Post
While this was sitting at the dealer I stopped in one night and poked around, they had the valve cover off and the number 6 rocker was loose. I thought this confirmed my suspicions of what was wrong, since this seems to be a common problem cylinder. After I started tearing into it, I noticed that the whole coil set was unplugged for the drive home. Now that I have the passenger cover off again, everything is back tight?? Could the shock of driving it unplugged have caused vibration to free the lifter? It seems very unlikely to me, but i dunno. ....
Thought about this while falling asleep last night. It's very possibly that the engine may have rattled the lifter loose, but unfortunately my brain went to the dark side. Wondering if the tech did something to release the lifter, saw he wasn't going to get paid, and impolitely left the harness unplugged? About deleted this after typing it, but just going to leave it there, I have good faith in humanity, just hate to think that way.

Quote:
Originally Posted by mkgearhead View Post
I don't know for sure. The DTC description says whenever a deactivation solenoid circuit fault is set the ECM will return to V8 mode and shut off the injector to that cylinder, causing a misfire. On a side note I'm working on a gen 5 right now that has one AFM lifter that won't lock in DOD mode, you should hear the knock this thing makes in V4. Runs fine in V8 mode.
Dammit man, guess they painted themselves into a corner w/ the AFM design and can't figure a way out? You'd think there would be a fix out by now (besides going old school).

I think I read about people unplugging the AFM in the past and not being successful, but cannot quote that, or link to it.. I'd try it but pretty sure you'd have to pull the intake to get to it the way the yukon's package tray envelopes the top half of the engine.
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Quote:
Originally Posted by Teeleton
Hot wiring is bad news.
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Old 01-10-2019, 09:35 AM   #17
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Alright, pulled the drivers side cover; all good there too.

Reassembled everything (left the AFM unplugged) and started it up. Not knock, no tap, no problems! I do still have a check engine light and the service traction and stabilitrac warnings, but I am assuming thats from the unplugged solenoid.
(you can reach the plug if you have the rear "shield" removed from the intake and the engine cover off.)

I don't want to drive it until I get the ECM programmed, but I think it's all good...

So, pro-tip, if you have a collapsed lifter; just drive 20 miles with the coils unplugged on that bank!! No fuss, no muss, instant fix!!!
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Old 01-10-2019, 10:44 AM   #18
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Lol, man, you won the lottery!!

Plug the AFM back in and drive the truck in D, NOT OD. I know 08+ have the 6L60-E, not sure what terminology they use for that shift selection. That will clear the traction and stabilitrak warnings, take the trans out of limp mode, and give you a real feel for any pertinent codes that may come up.

Great score, I'm jealous!

*EDIT* when you do get the truck tuned, tell them to lean out power enrichment, factory is really way too rich, it's ridiculous.

Mike, I remembered on my co-worker's truck tune, I bumped up idle because his truck would vibrate the pass floorboard in gear. Going up 50 rpm smoothed that out. I can send you my tune if you want to look it over.
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Quote:
Originally Posted by Teeleton
Hot wiring is bad news.
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Old 01-11-2019, 10:56 AM   #19
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Plugged AFM back in, drove a few miles up the road. Went through all 5 lower gears (left it in M5). All seems to be going great. Computer is in the mail to the tuner now. I can't believe it worked out this easily, but I'm trying to remain optimistic.

Cost breakdown:
Suburban -------------------------------------$1170.00
Tune with shipping ----------------------------- $60.13
3/8" Fuel line disconnect (couldn't find mine) - $3.99
Battery -----------------------------------------$200.00

Total ------------------------------------------ $1434.12

Best deal of my life - priceless!

Thanks to all for the help.
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Old 01-11-2019, 01:16 PM   #20
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you suck!

Great job man! You made out like a bandit on that one!
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Quote:
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Hot wiring is bad news.
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