Help with Unique issue with AFM.. DID I BREAK my engine?

[BG1988]

So I was downshifting into m4 and Now my engine no longer goes into V4 mode(stabilitrak came on for like a second ) i think i did it a little two fast and now the ECU is fudged up.....
No active faults on DIC for stabilitrak.... as my speed wasn't going down at a desired rate..(down hill off ramp)
I notice i had forgotten to plug in my AFM disable chip while on my way home only to notice v4 mode wasn't working at all..


Now V4 mode is permanently disabled.. and Deceleration fuel cut off doesn't work anymore too.... it's still injecting fuel like the old cars did back in the day..

121,200

the engine felt normal not rough at all Not even the tensioner pulley was making noise (not like it did before) Yeah i already ordered a replacement and replacement belt

has an active Check engine for the HV battery only


I'll be honest it does operate way smoother though none of that jerky DFCO

 

[Marky Dissod]

I was downshifting into m4 and Now my engine no longer goes into V4 mode
(stabilitrak came on for like a second ) i think i did it a little two fast and now the ECU is fudged up ...

The ecu being fudged up is not impossible, but incredibly unlikely.
It's far more likely that the ecu noticed something unexpected and threw up a code or codes.
What are those codes? You'll have little to no idea what needs diagnosing / fixing without those codes.

No active faults on DIC for stabilitrak ... as my speed wasn't going down at a desired rate
(down hill off ramp)
I notice i had forgotten to plug in my AFM disable chip while on my way home only to notice v4 mode wasn't working at all ...

If somehow, V4 mode is disabled by a fault, still a good idea to find exactly that fault.
Just because the DIC shows no active faults, does not mean there are no active faults.

Now V4 mode is permanently disabled, and Deceleration fuel cut off doesn't work anymore too.
it's still injecting fuel like the old cars did back in the day.
the engine felt normal not rough at all Not even the tensioner pulley was making noise (not like it did before) Yeah i already ordered a replacement and replacement belt
has an active Check engine for the HV battery only
I'll be honest it does operate way smoother though none of that jerky DFCO

If the only results are losing V4 mode and DFCO, you may decide to live with it.
Losing V4 mode seems like a good thing for sure - I'd still like to know WHY though.

Losing DFCO may be acceptable to you. I would not find it acceptable.
Either way, again, you have to do some more research to find out why.

 

[BG1988]

the engine does run far better though..I can feel the difference esp with the DFCO non functional

feels more like drive by wire then a E-throttle.

 

[Marky Dissod]

Anyone who still thinks the engine runs better WITH cylinder deactivation, has not been paying attention to statistics over an extended period of time. It's good that your V8 is not trying to be a V4 sometimes.

But how do you know this is permanent, if you don't know more details about what happened?
My curiosity would not be satisfied.

As for the loss of DFCO:
I used to drive a 2012 Yukon XL as a livery / taxi / rideshare vehicle in NYC as well as NJ, CT, and occasionally, even a bit further outward.
From personal experience, if your front brakes are thinner than you'd like / they should be
(NYC taxi / limo drivers with comfortable financial margins are so rare, most people will never find ONE)
having DFCO kick in to help slow the truck down may be better than a costly collision.

Again, I'd NEED to know more details about what happened.
I'd NEED to know WHY V4 mode and DFCO are gone.
Then I could make an informed decision about what I want to do about it, if anything.

Something besides the ECU may have broken, or slipped out of place, or something like that.
You're really not curious?
Hope this helps.

 

[BG1988]

Anyone who still thinks the engine runs better WITH cylinder deactivation, has not been paying attention to statistics over an extended period of time. It's good that your V8 is not trying to be a V4 sometimes.

But how do you know this is permanent, if you don't know more details about what happened?
My curiosity would not be satisfied.

As for the loss of DFCO:
I used to drive a 2012 Yukon XL as a livery / taxi / rideshare vehicle in NYC as well as NJ, CT, and occasionally, even a bit further outward.
From personal experience, if your front brakes are thinner than you'd like / they should be
(NYC taxi / limo drivers with comfortable financial margins are so rare, most people will never find ONE)
having DFCO kick in to help slow the truck down may be better than a costly collision.

Again, I'd NEED to know more details about what happened.
I'd NEED to know WHY V4 mode and DFCO are gone.
Then I could make an informed decision about what I want to do about it, if anything.

Something besides the ECU may have broken, or slipped out of place, or something like that.
You're really not curious?
Hope this helps.

I already stated what happen when this issue occurred...

I downshifted into M1-4 which is v8 only mode(for all 4 gears) to come to a stop (on a downhill off ramp )which a stabilitrak light came on activation i.e wheel slippage for about 1 one second or two ... Stopping speed needed to be increased due to a vehicle that was stalled out in traffic lane at the bottom of the off ramp...
I checked for codes again P0300 random misfire 'pending'

I see the issue 12.7 volts instead of 14.5-14.8v it should be at when engine is running there your problem fudgen battery connector

 

[BG1988]

Ok quick update P0304. Pending

 

[BG1988]

Ok. Cleared up the glitches. V4 mode has returned and dfco as well.. on a second time of having the battery disconnected reset the engine codes as well

 

[BG1988]

update everything seem fine now the misfire is gone...I did a drive cycle from work to home without issue..

long term Fuel trims are Better now
+3.9-5.6 Bank 1
+1.6-3.9 Bank 2

 

[j91z28d1]

so you are using your shift buttons to down shift instead of braking and that loosened a battery clamp?

my quick latch clamps don't move a bit, habe you checked your motor mounts? makes me wonder if the motor is moving around enough to tug on a wire really hard.