Yukon Denali issue

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DGMCTRUCK

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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.
 
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j91z28d1

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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.
 

j91z28d1

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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.

PXL_20241123_210957522.MP.jpg


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

PXL_20241123_211004815.MP.jpg


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

j91z28d1

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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.
 

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