4wd updates to ecm

XrivaInc · February 10, 2016

Mine was also done at an oil change - in mid November. I've not been pleased with the changes, however. I'm noticing a few issues that I wish could be reverted:

1) MPG - dropped significantly: 10% on highway, 20% around town. I was getting ~19mpg highway @ 73mph, ~16mpg town. Now ~17mpg and 12mpg.

2) Transmission lurching - lots more shifting is occurring. Some of those come with a clunk as well. It didn't seem to happen as much before.

3) RPM higher when coasting - Maybe this is contributing to the lower MPG? It doesn't coast as well when releasing accelerator pedal. It seems to slow down quicker, and the RPMs are higher. This is also noticable @70mph on rolling hills with cruise. In watching the DIC avg mpg display, it seems that any reductions from going uphill aren't gained back when going downhill. But before the 4wd update, they did gain back (and the RPM was much lower going down the hill).

I suppose the update is to blame for more shifting, etc, as it seems to be trying to be ready (i.e. downshifting) for a press of the accelerator - thus the quicker response others are reporting. I was okay (learned to live with) with the behavior before, but I can also live with the more responsive improvements. And that might be what is keeping the RPMs higher when coasting in town. But I think it downshifts too quickly and it should wait until I am almost stopped at a stoplight, etc. And why keep the RPMs high when going down a hill in cruise?

As for the MPG, I can't believe that winter fuel blend here in the midwest would be the culprit for all I'm seeing. Especially since I went through the previous winter (2014-2015) without seeing this much drop.

Has anybody else seen this? Any suggestions? The dealer gave me the usual SB on "clunk" and said it was all normal and wouldn't look into it any further.

Jimmyc1182 · February 24, 2016

I just got a call from the dealership about this recall. The timing is a little late I guess. My truck did this to me last night on the way home from work. I tried switching in and out of 2wd, 4wd and auto.tried going back and forth and it wouldn't do anything. I will have to get this taken care of.

ghobbs26 · May 16, 2017

hello there i know this probably has nothing to do with the 4wd topic but i have a 2016 chevy 1500 with the 5.3 and I just hit 16,000 and my ECM and Battery were bad and left me stranded on the highway. First I had all kinds of lights come on and My A/C started blowing hot and then i went into limp mode and my steering was acting up and it told me to service my traction control, stabilitrak, and my anti locking brakes needed service plus my oil gauge and my temp gauge stopped working as well so i turned my truck off and then tried to restart it and it wouldn't even crank over at all and then i had no power at all in my truck. I had it towed and they said they replaced my ECM and my battery since they were both bad. I just don't get how the ECM goes bad that quickly has any one else had any problems with their ECM??

2strokesmoke · May 16, 2017

hello there i know this probably has nothing to do with the 4wd topic but i have a 2016 chevy 1500 with the 5.3 and I just hit 16,000 and my ECM and Battery were bad and left me stranded on the highway. First I had all kinds of lights come on and My A/C started blowing hot and then i went into limp mode and my steering was acting up and it told me to service my traction control, stabilitrak, and my anti locking brakes needed service plus my oil gauge and my temp gauge stopped working as well so i turned my truck off and then tried to restart it and it wouldn't even crank over at all and then i had no power at all in my truck. I had it towed and they said they replaced my ECM and my battery since they were both bad. I just don't get how the ECM goes bad that quickly has any one else had any problems with their ECM??

Please read all of this thread, maybe you had/have a loose ECM ground.....many others had the same problem you are describing.

http://www.gm-trucks.com/forums/topic/200566-codes/

Thxs