Stuck in v4 from a start while towing

Popo1984 · May 28, 2019

I recently towed my travel trailer about 100 miles back home. All was well and had no issues the entire way. a few miles from home i stopped at a red light, when the light turned green i started to move and noticed it seemed like it was running rough and i really needed to give it some gas to start moving. I looked down at the display and didn't see any check engine lights or reduced power warnings but i showed that it was in V4 mode. I got through the intersection nd let off so it could coast for a second. then i gas it a good amount of pedal and it worked as it should from then on out. Anyone every experience this?

Also just FYI its not hot here in Texas yet id say it was 80-85 the whole way towing back from Livingston to Pasadena. My trans temp maintained 192-194 the entire way home. Im towing a 28" Jayco about 7000LBS. 5.3, 6L80E.

1SLOW1500 · May 28, 2019

Something is wrong the pedal demand should have turned v4 off.

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Popo1984 · May 28, 2019

Ive towed several times with this truck even heavier loads but have not experienced this before. The truck is stock except a muffler delete. I leave thursday on a 600 mile round trip so ill see if this happens again.

Side question do these trucks need software updates from time to time? Are they done OTA or when vehicles are take in for service?

Mikebtte · May 28, 2019

Mine would act this way when I had the AFM turned on. When giving it gas slowly I could hold the V4 for a good while.

My biggest issue is I did not think V4 was active at idle. I was pretty sure the vehicle had to be in motion for it to activate.

CKNSLS · May 30, 2019

It happen to you only once? OR-multiple times?

Just want to be clear here.

Paintor · May 30, 2019

Throw it in Manual if it happens again. Shift with toggle button.

Donstar · May 30, 2019

Phone your local GM dealer and get it checked out. They may have a simple fix or most likely will tell you it's "normal" or "can't replicate problem". The real benefit of going through the dealer is that you will have a record with GM about your concern. My experience with GM service is that they use a systematic step by step approach to deal with odd vehicle behavior. The first step is often trying to get you to accept that its normal. If the problem persists, they'll do "something". When you take it back for a third time, things get replaced.

HeySkippyDog · May 30, 2019

I've towed with mine plenty, not quite as much weight, but mine stayed in V8 unless I was cruising. I did have it in Tow/Haul mode though. Did you?

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Popo1984 · May 30, 2019

So that was the one not time it’s happened. I made it from Pasadena to pedernales falls this morning with out it happening and I did way more start and stop driving on this route. Maybe it was a fluke, if it happens again I’ll definitely take it to the dealer. Yes it was in tow haul

mode.

What at all does tow haul mode do? I know it raises shift pints but are there any other things it changes?

HeySkippyDog · May 30, 2019

So that was the one not time it’s happened. I made it from Pasadena to pedernales falls this morning with out it happening and I did way more start and stop driving on this route. Maybe it was a fluke, if it happens again I’ll definitely take it to the dealer. Yes it was in tow haul
mode.

What at all does tow haul mode do? I know it raises shift pints but are there any other things it changes?

It raises shift points, and I believe that translates to a higher perceived demand and longer periods in V8.

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Popo1984 · June 7, 2019

Well after over 600 miles this last week it didnt have this issue pop up again.

HeySkippyDog · June 7, 2019

Well after over 600 miles this last week it didnt have this issue pop up again.

Did you try using Tow/Haul with the trailer? What did you do different?

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Popo1984 · June 7, 2019

I always use Tow/ haul when towing. Didn't do anything different.

Paintor · June 7, 2019

VLOM needs sufficient oil pressure to turn off V4, and pump your lifters back up for V8.

https://www.melling.com/wp-content/uploads/2018/03/Melling-tech-bulletin-on-GM-LS-Deactivation-Lifter-Issues-3.1.18-1.pdf

HeySkippyDog · June 9, 2019

Everywhere Paintor goes is another doom and gloom post about V4 mode. I don't even have to open the thread to know that's what he's crying about.

You know that the article you posted refers to GM LS engines with AFM, right?

The AFM K2 trucks don't have LS motors. The LS AFM was the previous generation and those had some bad problems.

Ecotec is another engine.

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