2015 LML hard down shift

[NC-smokinlmm]

I sometimes wonder if the lb7 and lly engine codes got getter fuel economy bc they had a bosch computer controling the injectors instead of gm's ecu. Seems they dont care as long they make more money. Its bc of stupid things like this that make me think Cummins for my next rigg...

 

[Cougar281]

I sometimes wonder if the lb7 and lly engine codes got getter fuel economy bc they had a bosch computer controling the injectors instead of gm's ecu. Seems they dont care as long they make more money. Its bc of stupid things like this that make me think Cummins for my next rigg...

Except the LBZ & LMM used a Bosch ecm as well .

Edit: actually, the lb7 & lly didn't have Bosch ecm's....

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[NC-smokinlmm]

Except the LBZ & LMM used a Bosch ecm as well .

Edit: actually, the lb7 & lly didn't have Bosch ecm's....

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The lb7 and lly injectors are controlled by an ficm. Not the ecu, is what I was pondering about...

 

[Cougar281]

The lb7 and lly injectors are controlled by an ficm. Not the ecu, is what I was pondering about...

No, not exactly. The injectors are DRIVEN by the FICM, but they are CONTROLLED be the ECM. The FICM can't/won't fire the injectors without a command from the ECM. The LBZ/LMM just went from a Delphi ECM controlling the Bosch FICM to the Bosch ecm doing it all but at a lower voltage.

I'd say my truck as a LBZ has gotten better mileage now than it did when it was a LLY. Granted, not HUGE better - probably 1-4 mpg better - but still better. I think a LOT has to do with tuning and driving style. If I baby it, I get noticeably better mileage than I do if I drive like normal.... I usually drive it like I stole it and it's hard keeping my foot out of the loud pedal .

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[duratothemax]

The lb7 and lly injectors are controlled by an ficm. Not the ecu, is what I was pondering about...

As far as I know, the FICM on a Duramax doesnt do any of its own adjustments, other than maybe some minor filtering/conditioning for signal noise on the replicated CKP sensor signal wire and injector control signal wires...its literally just there to provide a high-current/voltage injector driver for the [delphi] ECM, because the ECM does not contain any high-current injector driver circuitry of its own.

In other words, its not like a ford, where the FICM actually does do some additional stuff and decision making.

Jon (fingers) would probably have more info on this.

Ben

 

[Papuller86]

sorry to dig up a old thread but, im having the same issue since about 7000 miles on my 2015, i told the dealer ship about it abd they did nothing at first, a year later its gotten worse and more frequent, i even have a oil leak problem, this time the "claim" they fixed the oil leak, said it was a loose pan but how in the hell does oil get above the starter from the pan

 

[Papuller86]

sorry to dig up a old thread but, im having the same issue since about 7000 miles on my 2015, i told the dealer ship about it abd they did nothing at first, a year later its gotten worse and more frequent, i even have a oil leak problem, this time the "claim" they fixed the oil leak, said it was a loose pan but how in the hell does oil get above the starter from the pan

 

[Digmax]

I had a 13 model that was in the shop 6 weeks out of six months for that same leak, they never did find it..... so traded it

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[Chevy1925]

I guess ill update on my dads truck.

he has 22k on it now and i just drove it last week. cant say i felt any bad down shifts or issues i didnt like. he cant remember when they quit but clearly they stopped early enough to keep him from taking it back to the dealer.

 

[Chevy1925]

So just to update an old thread of mine.

Harsh downshifts are only when the truck is in regen and idle elevates a bit. GM won’t do anything for him. It’s one of those “oh that’s the first we have heard. Blah blah blah”. Told him I could take care of that pretty easy but he doesn’t want to go down that road lol. Just a little annoying to him. Maybe when his first emission issue comes up