4x4 stuck causing drastic MPG loss

So I have a 2017 DC4x4 and I have been getting somewhere around 12.5 mpg. I was stressing it because everyone was getting 17-19 mpg on average. AND I know about driving conditions but I dont drive aggressive nor do I think I would average 5-7mpg less if I was trying to get it up.. I kept racking my brain to figure it out. I randomly heard a noise when I went over a steep incline/decline, like a grinding or the drive train not functioning correctly. It made me wonder it I had a hub that was not correctly locked or the 4x4 did not disengage. I took my truck to the dealer for the noise and brought up my concern to them, including the head tech there. I had a 20 min conversation with him... he told me it was the mud flap and my truck was getting 19mpg... he is full of crap. my truck was getting 12/13 on average. the eco said that and the math on fill up confirmed it.

when I brought the truck home, after they did nothing for the noise or mpg, I started playing around with the 4x4 and engaged and disengaged it several times... and one of the times i heard a noise that sounded just like the one I heard while driving over an aggressive driveway. After the noise it would engage/disengage fine!!! and guess what, the noise was gone when I went over the driveway and my MPG shot way up!!! almost to 21/22. at one point on the highway i was getting 24/25... so moral of the story... There are a few people that have complained like I have about the mpg being so low.. I suggest you play with the 4x4 several times and make sure to do it in neutral when doing so. I think people play with the trucks and buttons at the dealer and they dont care when they deliver it... I hope this helps you! btw I havent had the chance to take mine off road so I didnt even think the 4x4 could be the issue until I remembered my manual hubs on my 89 toyota... dont forget to unlock!!

 

Hopefully you didn't do any damage driving around making turns in 4 wheel drive.

 

That was my first thought

 

yeah, that was my main concern. I brought it in around 500/600 and reported issues... shift issues. low fluid. Noise from the UCA's. and now this crap.... but my truck seems to be doing well and im pretty happy with it right now! till the next thing breaks haha. I hope they give me an extended warranty.

 

Not sure if serious...

If 4hi was indeed engaged then the green indicator light on the dash would've been lit. Did you not see it or..?

 

no light and it wasnt fully engaged or disengaged... that was the problem leading to the grinding noise and mpg....

 

Maybe the transfer case is stuck. Only way he knows its stuck on 4x4 is to lift the whole truck up in the air and put it in drive/reverse.

 

Your truck would drive like crap if the 4wd was engaged on the pavement. It would not be easy to turn and you'd more than likely brake something. I highly doubt it is the 4wd. Not saying there isn't an issue I just doubt that's the problem.

 

well if they actually did their jobs they would have actually looked at it. I even asked them to look at it.

 

Why the heck does my trip information not show average trip mpg? Been going thru the menu and haven't seen any option. It only shows distance traveled and distance to empty.

 

I agree, how can you not notice it being in 4wd on dry pavement with or without the light. You would have been hopping all over the place in a tight turn like mentioned above.

 

You'd be surprised on how many people actually do their job...

I would check it myself. If it is stuck, have it towed to the dealer. Then they'll pay attention. Just say the words "Toyota Corporate customer service" and the service manager will be all over it.

 

Instead of scrolling left and right scroll down.

 

I'm not 100% fluent in the operation of the 4wd system electronics but is it possible that either the t-case or front axle could be partially engaged, tricking the ECU into thinking the 4wd system is not engaged at all? That might explain his issue.

 

I'm not sure that's the issue either. If it was in 4WD, you would have KNOWN if you made any turns. The binding and hopping would have been obvious.

 

The turn radius would be way off in left field but i can see that you might not notice. Also it would take quite a bit of binding to really do damage.
I drove my work truck in 4hi for a day without noticing until i pulled a uturn in a parking lot. It happens.

 

I wasnt in 4hi or 4low... my 4x4 had not fully disengaged. the system thought it had but it hadnt. so when I went over a rough incline/decline I heard the Tcase rubbing. I would notice if I was driving around with it on.