Getting an ECM update on my 14' silverado right now for transmissi

[Steve1199]

Note up front - Don't shoot the messenger. Just stating what i've been told this morning while at dealer. Sitting in dealer waiting on truck right now.

 

At the dealer for my 15K oil change. noted the continued clunking, thunking, shuddering up-shifts, clunks of transmission shifting even while coasting, getting transmission "confused" when getting back on the throttle while coasting in V4 mode and truck shuddering while hunting for a gear and switching to V8 mode.

 

did a drive with the service tech, he heard a few thunks from rear end. He explained these as the partially the spacing in the rear end and transmission gears, and since there is some natural spacing as they can't be perfectly locked, you can get into positions where there is more or less slack at varying times, and can catch a time of more slack combined with throttle application that results in a thunk.

 

While talking about V4 mode, he mentioned that that takes effect at 35mph, and i corrected him and said that no, my truck will run V4 mode down to 8mph, and if i'm accelerating gently leaving my house in the morning, as soon as i'm out of my driveway (truck on for less than 1 minute) the truck will switch to V4 as soon as i pass 8mph and stay in V4 as i accelerate. He seemed surprised by this.

 

After talking to the shop manager, they said there is a Service Bulletin out there about issues like my transmission related issues and thunking i've mentioned. It referenced an ECM update as a possible solution. He also said that there is a recall out there for some other trucks (he did not say what trucks fell under the recall), and as part of the recall, it involved upgrading the ECM firmware. He told me that the firmware upgrade to the ECM was something that they could do to my truck, even though my truck did not fall under the recall in an attempt to see if it helped my issues.

 

Of note, he said the ECM update was an update that could not be rolled back from, ie, if it didn't help or caused issues, then there was not going back.

 

He did say that they've done this upgrade before, and those who have had it, have not come back saying they were still having the same issues still.

 

So, dice rolled. i'm having them update the ECM firmware and will report back with any documents listing numbers or reference material for the ECM update as well as letting everyone know how the truck drives.

 

hope this helps. Again, don't shoot the messenger, just trying to regurgitate what the service tech just told me.

[Silverado-Hareek]

Note up front - Don't shoot the messenger. Just stating what i've been told this morning while at dealer. Sitting in dealer waiting on truck right now.

 

At the dealer for my 15K oil change. noted the continued clunking, thunking, shuddering up-shifts, clunks of transmission shifting even while coasting, getting transmission "confused" when getting back on the throttle while coasting in V4 mode and truck shuddering while hunting for a gear and switching to V8 mode.

 

did a drive with the service tech, he heard a few thunks from rear end. He explained these as the partially the spacing in the rear end and transmission gears, and since there is some natural spacing as they can't be perfectly locked, you can get into positions where there is more or less slack at varying times, and can catch a time of more slack combined with throttle application that results in a thunk.

 

While talking about V4 mode, he mentioned that that takes effect at 35mph, and i corrected him and said that no, my truck will run V4 mode down to 8mph, and if i'm accelerating gently leaving my house in the morning, as soon as i'm out of my driveway (truck on for less than 1 minute) the truck will switch to V4 as soon as i pass 8mph and stay in V4 as i accelerate. He seemed surprised by this.

 

After talking to the shop manager, they said there is a Service Bulletin out there about issues like my transmission related issues and thunking i've mentioned. It referenced an ECM update as a possible solution. He also said that there is a recall out there for some other trucks (he did not say what trucks fell under the recall), and as part of the recall, it involved upgrading the ECM firmware. He told me that the firmware upgrade to the ECM was something that they could do to my truck, even though my truck did not fall under the recall in an attempt to see if it helped my issues.

 

Of note, he said the ECM update was an update that could not be rolled back from, ie, if it didn't help or caused issues, then there was not going back.

 

He did say that they've done this upgrade before, and those who have had it, have not come back saying they were still having the same issues still.

 

So, dice rolled. i'm having them update the ECM firmware and will report back with any documents listing numbers or reference material for the ECM update as well as letting everyone know how the truck drives.

 

hope this helps. Again, don't shoot the messenger, just trying to regurgitate what the service tech just told me.

 

You've described my truck exactly. Especially the switching to V4 after just leaving my driveway which seems to be a new issue after I put in synthetic oil and did a BG induction service. I chalked it up to the engine running more efficiently now that it's clean and with synthetic oil, but I can't be sure that this is exactly when it started. I noticed the 2015 loaner I was driving the last couple of days switched into V4 much further down my street after leaving in the morning.

 

Please keep us posted!

[Rawyzf]

Please do report back, can't wait to hear what if it helps.

[Steve1199]

Also passed to me some other info. this may be known already or not. just posting what they told me. not saying i'm smart enough to fact check what he said, just passing what was told to me.

 

Tow haul mode - de-activates the servos used in the torque converter that are used to manage the plates in the torque converter. these servos manage the torque converter packs to improve fuel mileage. tow haul disables these servos.

 

Coasting - at some speeds, the transmission will actually basically go into a form of neutral to maximize gas milesge, which, when getting back on the gas, can partially lead to some of the clunking or behaviors as the transmission works to get back into gear and drive, which can be compounded by a switch from V4 up to V8.

 

Again, just words the dealer told me.

[Steve1199]

 

You've described my truck exactly. Especially the switching to V4 after just leaving my driveway which seems to be a new issue after I put in synthetic oil and did a BG induction service. I chalked it up to the engine running more efficiently now that it's clean and with synthetic oil, but I can't be sure that this is exactly when it started. I noticed the 2015 loaner I was driving the last couple of days switched into V4 much further down my street after leaving in the morning.

 

Please keep us posted!

Yeah, the service tech seemed notably surprised that my truck was going to V4 as soon as i got going and at such a slow speed as well. he mentioned more than once that V4 mode becomes active at 35mph.

 

Also, he said that neither the recall nor the Service bulletin applied directly to my truck (2014 Silverado 5.3, CC, Z71), but that it was on similar trucks and the symptoms were basically the same.

[joeglock40]

Idk about the coasting part with it going "neutral" cuz when i coast i can here the engine down shifting n feel some engine breaking. I have a hypertech in my truck tho so idk if that'll change it up

[Rawyzf]

Did he mention what trucks the SB applied to?

[Silverado-Hareek]

Yeah, the service tech seemed notably surprised that my truck was going to V4 as soon as i got going and at such a slow speed as well. he mentioned more than once that V4 mode becomes active at 35mph.

 

Also, he said that neither the recall nor the Service bulletin applied directly to my truck (2014 Silverado 5.3, CC, Z71), but that it was on similar trucks and the symptoms were basically the same.

 

 

The truck doesn't need to be going 35mph for V4 to engage. Anything above 5 mph and V4 can activate if conditions are right(i.e. proper engine temp, coasting and not under a load, etc.). Mine just seems to be doing it sooner than it used to when I left my house. I can't drive 35mph on my street the max I ever go is 20 and V4 will always engage when conditions are right. I just don't think it should do it when I'm still accelerating even if I'm only lightly pressing the throttle.

 

Idk about the coasting part with it going "neutral" cuz when i coast i can here the engine down shifting n feel some engine breaking. I have a hypertech in my truck tho so idk if that'll change it up

 

Yep these trucks will downshift if you let it coast which I REALLY hate.

[Steve1199]

Idk about the coasting part with it going "neutral" cuz when i coast i can here the engine down shifting n feel some engine breaking. I have a hypertech in my truck tho so idk if that'll change it up

I agree.

 

i can feel and hear my truck shift or change gears while coasting. they said it didn't do it all the time, but that at times it would.

Did he mention what trucks the SB applied to?

No. i plan on asking when i get a chance.

[Silverado-Hareek]

Another weird thing I've noticed....If I'm cruising down the interstate with the accelerator pedal slightly pressed and I'm in V4, the truck will switch to V8 immediately if take my foot OFF the gas. Anyone else notice this on their rig?

[Steve1199]

 

 

The truck doesn't need to be going 35mph for V4 to engage. Anything above 5 mph and V4 can activate if conditions are right(i.e. proper engine temp, coasting and not under a load, etc.). Mine just seems to be doing it sooner than it used to when I left my house. I can't drive 35mph on my street the max I ever go is 20 and V4 will always engage when conditions are right. I just don't think it should do it when I'm still accelerating even if I'm only lightly pressing the throttle.

 

 

Yep these trucks will downshift if you let it coast which I REALLY hate.

 

I was just given a document by the dealer detailing V4 mode activation requirements.

 

Document ID #:3137385 - Cyclinder Deactivation Active Fuel Management System Description. (i can try and scan and upload later if needed)

In this document, it states, for V4 Activation -

Engine running for more than 30 secdons

RPM between 700 and 2800

Oil pressure 27-66psi

coolant temp between 100-264 F (My truck would operator V4 outside this range)

Oil temp 61-263 (My truck would operator V4 outside this range)

throttle angle less than 6%

Ignition voltage greater than 11 V

Transmission is not in First, Second or Reverse (My truck seemed to activate V4 in every gear but reverse)

Vehicle Speed is greater than 25 kph (15.5 mph) (My truck would operate V4 down to 8mph both accelerating and decelerating)

Brake booster pressure more than 6psi

Vehicle not in fuel shut off mode

vehicle not in heater performance mode

vehicle is not in tip in bump acceleration mode

vehicle is not in oil aeration mode

vehicle is not in low range

Another weird thing I've noticed....If I'm cruising down the interstate with the accelerator pedal slightly pressed and I'm in V4, the truck will switch to V8 immediately if take my foot OFF the gas. Anyone else notice this on their rig?

yes. mine does that. not ever time, but i have seen it do that while on the highway.

[Rawyzf]

 

I was just given a document by the dealer detailing V4 mode activation requirements.

 

Document ID #:3137385 - Cyclinder Deactivation Active Fuel Management System Description. (i can try and scan and upload later if needed)

In this document, it states, for V4 Activation -

Engine running for more than 30 secdons

RPM between 700 and 2800

Oil pressure 27-66psi

coolant temp between 100-264 F (My truck would operator V4 outside this range)

Oil temp 61-263 (My truck would operator V4 outside this range)

throttle angle less than 6%

Ignition voltage greater than 11 V

Transmission is not in First, Second or Reverse (My truck seemed to activate V4 in every gear but reverse)

Vehicle Speed is greater than 25 kph (15.5 mph) (My truck would operate V4 down to 8mph both accelerating and decelerating)

Brake booster pressure more than 6psi

Vehicle not in fuel shut off mode

vehicle not in heater performance mode

vehicle is not in tip in bump acceleration mode

vehicle is not in oil aeration mode

vehicle is not in low range

 

yes. mine does that. not ever time, but i have seen it do that while on the highway.

 

Wow, that is suprising. They must not QA thier work based on that document. I have my dashboss and it shows gear/speed, etc. I know for a fact that I have been in 4cyl mode under 15mph and in 2nd gear. I'll have to snap a picture of that for them.

[Steve1199]

For V4 deactivation from the above stated document:

 

Engine coolant out of range

engine vacuum out of range

brake booster vacuum out of range

transmission gear incorrect or shift in progress (my truck has held V4 through upshifts and downshifts before)

accelerator out of range (at times, i feel i have pressed more than 6% on the accelerator and stayed in V4 mode)

oil pressure or temp out of range

engine speed out of range

vehicle speed out of range

minimum time in V8 not met

max time in V4 exceeded

decel fuel cutoff is active

reduced engine power is active

torque management is active

catalytic converter is over temperature protection is active

piston protection is active, knock detected

cylinder deactivation solenoid driver circuit faults

[nadrojcote]

I had some bad clunking/thuding when shifting gears. It's partially the TCM programming, but mostly was due to our weak rear leafs that have no clamps on them. I clamped my rear leafs in front of the axle to reduce axle wrap so that my yoke wasn't thuding and voila, my shifts are much smoother now.

[fondupot]

Another weird thing I've noticed....If I'm cruising down the interstate with the accelerator pedal slightly pressed and I'm in V4, the truck will switch to V8 immediately if take my foot OFF the gas. Anyone else notice this on their rig?

 

This would be fuel shut off mode. Basically coasting...AFM disables when in fuel shut off mode.

 

I am also gonna be installing leaf straps like projectsummit did.