2012 Hybrid Yukon Denali major issue. Need help from the experts

[DGYukon]

More stored data

 

[DGYukon]

More data

 

[DGYukon]

More data

 

[DGYukon]

Module Scans

 

[DGYukon]

Module Scans

 

[DGYukon]

what I was meaning is I think it shutting off on you a year or so ago could be something different than happened this time. I've never seen an engine damage warning. is that on the dash display? makes me wonder what triggers that warning and how the tranny would make it think the engine is damaged.


man that does sound pretty bad. I might have missed it but how many miles? these transmission seem pretty common to go 250k or more miles.

These trannys are bit of a mystery and no one really rebuilds them. I talked to a retired gm tech that said he went to class for these when they came out. they spent 2 days on the transmission and then said but don't worry about any of that, you won't be rebuilding these. if they are bad gm engineers want them back and will send new ones in.
A used unit seems to be the only real way to get one these days. I've seen some on Facebook market for as low as 600$. they do have 2 electric motors in them, but they run kinda all the time doing different things. I honestly do not know if one could have a issue and lock up the tires like that. the transmission control module is inside the tranny and the shift linked is a cable. so I don't know if a can bus failure could cause this or not, but I'd hazard a guess that it shouldn't be able to. I guess it could have also engaged a lower gear at the wrong time too, like say downshift to 1st while doing 50. but I just don't know enough to say.

These don't have a torque converter like a normal tranny but there is a flex plate type of thing where a fly wheel would go that transfer power from crankshaft to transmission input shaft. maybe it broke that?

if you pull the dipstick and put it on a clean towel, do you see any metal? you could pull the pan and look for metal on the magnet inside too. Just be careful 14qt of fluid all come running out. makes a mess if you're not ready for the amount.


so for the codes, I guess you tried clearing them? did they come back? if so which ones? are you able to communicate with the modules with your scanner right now? what scanner do you have? does it show any live data from the transmission?

sorry, all I have is questions, no real answers. for the short time it's running, have you tried putting it in gear and see if it moves?


I fully understand wanting to keep it. I like mine a lot and since I'm basically a mechanic by trade. I hope I can fix whatever to keep mine going too. and I think I can fix most things, as I've read tons of posts and threads about issues to try and understand what all can go wrong. mine has been pretty solid thankfully, just the normal stuff for this generation and I'm Bata testing a different hybrid battery type right now that seems to be going well so far.
the transmission being the one thing I worry about that I can't fix. I've kept my eye out for a used one local, just to pick up as a spare if the day comes. I have read of some wearing out and slipping, but never once have I seen anyone post anything about one exploding internal like yours might have done.

It has 140,000 ish miles currently. I started it today and it will drive in the driveway while the engine is cold and not trying to run on the electric motors. Still in limp mode and won’t go above 3k rpms.

 

[j91z28d1]

hmm so just looking ******(you can't type quick ly here? odd word to sensor lol) , I would disregard all the U codes, the network went down forsure. that's about all you can learn from those, and the ones requesting the mil light on. those are generic. the individual modules cants turn on the mil light themselves, they have to request the ecm to do it for them. that's all just redundant and doesn't say much.

in the engine data, few things I see. it looks like your were diving along and the 12v battery voltage was 11.9. that's very low like truck not running key on low. should be high 13s up to 15s sometimes.

it shows rpm 0, the maf shows zero airflow, mph and spark advances all 0. like the engine wasn't running when it captured that freeze frame data. I'm not sure exactly what gust means, but if you were above 30mph the engine should have been running.


where it shows 8 dtcs on the transmission control module, I'm sure one will be a U for communication and one for mil request. but can you read the other 6 codes? they might be more specific. same with the ecm codes. it says 4, maybe there's 2 of them useful?


curious if you've tried clearing theses and they reset or is this the first batch from what it locked up the wheels.

 

[DGYukon]

hmm so just looking ******(you can't type quick ly here? odd word to sensor lol) , I would disregard all the U codes, the network went down forsure. that's about all you can learn from those, and the ones requesting the mil light on. those are generic. the individual modules cants turn on the mil light themselves, they have to request the ecm to do it for them. that's all just redundant and doesn't say much.

in the engine data, few things I see. it looks like your were diving along and the 12v battery voltage was 11.9. that's very low like truck not running key on low. should be high 13s up to 15s sometimes.

it shows rpm 0, the maf shows zero airflow, mph and spark advances all 0. like the engine wasn't running when it captured that freeze frame data. I'm not sure exactly what gust means, but if you were above 30mph the engine should have been running.


where it shows 8 dtcs on the transmission control module, I'm sure one will be a U for communication and one for mil request. but can you read the other 6 codes? they might be more specific. same with the ecm codes. it says 4, maybe there's 2 of them useful?


curious if you've tried clearing theses and they reset or is this the first batch from what it locked up the wheels.

Sorry these are the codes I got today after I cleared the codes from the other day. Truck was just in the driveway today at the time. When I started the truck today the battery voltage went to 15 then mid 14’s

 

[j91z28d1]

It has 140,000 ish miles currently. I started it today and it will drive in the driveway while the engine is cold and not trying to run on the electric motors. Still in limp mode and won’t go above 3k rpms.

I'm over 165k on mine and the tranny fluid sample tests good. so it would be horrible luck for your tranny to blow up at 140k.


so I'll attach what my software says for limp mode for these trucks. I'm hoping you have one of these P code dtc's in your ecm. that would help give some direction as to why it's in limp.




and what the tranny defuals to when it's in limp mode.




hopefully those arw readable. I'm just on my phone and can't tell on my end.

 

[j91z28d1]

Sorry these are the codes I got today after I cleared the codes from the other day. Truck was just in the driveway today at the time. When I started the truck today the battery voltage went to 15 then mid 14’s

ahh, so that's helpful. I was thinking this was from the first event. so we know the Communications Network is still down, so that's not intermittent or one time thing.
since you have that replacement module coming. I hope that fixes it.
there's actually 2 networks, I high speed and a low speed. do you have a ohm meter?

my guess is high speed is down, since you can still see some info from modules besides the ecm. I'd be curious if you can retrieve it those 4 ecm codes and 8 tcm codes.

edit, the 11.9v probably means it sets the codes before the engine even started, at first key on.