Intro and MDS Question - 2016 Big Horn

[Rampant]

Maybe it's the difference between the 1500 and 2500 or 5.7 and 6.4. my eco light comes on without MDS enguaged, which it appears they are not tied together. Don't k own about t/h mode, haven't checked that out.

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Right, that's long been established. But he has a 6.4, so it's obviously a 2500 or 3500 he's talking about.

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[Jimmy07]

Can you prove the top two things? Because I'll tell you what, I've used TH mode a LOT and the MDS has never kicked in one time. Also, the the eco light has never came on one time without the MDS kicking in. They are absolutely linked in my truck. If you have a CAI on a 6.4, there is zero chance you will mistake the sound it makes when MDS kicks in.

I made those clarifications strictly for the OP in relation to his 5.7. Our 6.4’s with the 6 speed are indeed different, but why make it more confusing for him than it has to be. But, yes, tow haul will disable MDS on ours, as will ERS. The ECO light situation remains the same for us, though. When not in tow haul, and not utilizing ERS, you can definitely get the ECO light to come on when MDS is not activated.

 

[Rampant]

I made those clarifications strictly for the OP in relation to his 5.7. Our 6.4’s with the 6 speed are indeed different, but why make it more confusing for him than it has to be. But, yes, tow haul will disable MDS on ours, as will ERS. The ECO light situation remains the same for us, though. When not in tow haul, and not utilizing ERS, you can definitely get the ECO light to come on when MDS is not activated.

I've had my truck for over two years now, and that has never happened. My truck has never been to a dealer at all since I bought it new, so maybe there was an update? Maybe they updated in 2017s? Do you have an open-element cold air intake?

 

[Jimmy07]

I've had my truck for over two years now, and that has never happened. My truck has never been to a dealer at all since I bought it new, so maybe there was an update? Maybe they updated in 2017s? Do you have an open-element cold air intake?

No. Everything stock powertrain wise.

 

[Rampant]

No. Everything stock powertrain wise.

Well when you have a CAI on a 6.4, the noise it makes when MDS kicks is impossible to ignore. I'm very **** and watch my gauges like a hawk. Since I put 35s on it, the MDS hardly ever kicks in anyhow. But when it does, you know it for sure and you can watch the light go on and off with it. The light never comes on without the MDS in my truck.

 

[Jimmy07]

I hear ya, and believe me, I know exactly when MDS is activated on mine. The easiest instance when the light will come on without MDS is when you’re cruising at about 35 and come to a stop light and let off the gas. You’ll notice the ECO light come on and your “current MPG” will go to 99. That’s not because MDS is active, but rather, fuel has been cut off from all injectors.

 

[Ramit355]

Can you prove the top two things? Because I'll tell you what, I've used TH mode a LOT and the MDS has never kicked in one time. Also, the the eco light has never came on one time without the MDS kicking in. They are absolutely linked in my truck. If you have a CAI on a 6.4, there is zero chance you will mistake the sound it makes when MDS kicks in.

You are Correct .I have had two 8 speed Rams both 5.7 (with 3.92 rear gears equipped for towing.) Pull camper, Pontoon boat, Flat bed duel axle trailer. Tow haul button disables your MDS which automatically turns off ECO. Saving fuel towing is usually not a priorority. The Tow Haul should be utilized on all towing so the mds is turned off to lower the heat on the Transmission. With that said if you tow with out engaging tow haul you will remain with MDS engaged and doubtful the ECO light will illuminate unless your going down grade. When you pull loads the Transmission will select what gear is needed with out pushing the + or _ for gear selection on steering wheel. The gear selection is helpful when towing heavy loads in Hilly terrains by selecting the next lower gear to stop the Transmission from "Hunting" a lower gear in and out creating excessive heat to the transmission.

MDS is just like old school overdrive,except now when over drive is selected electronically by the MDS it will be deactivating 4 cylinders at the same time by the use of solenoids. In effect the MDS turns off the same 4 cylinders each time the ECO comes on indicating such.Never ever pull loads with over drive engaged or MDS so it remove excessive heat from the transmission clutches or taking heat of Clutch plates on standard shifts.

 

[Hemi Lonestar]

My ECO light never comes on when I have the MDS disabled no matter how I’m driving, my pedal position or grade. My MDS does come on in tow haul mode though, just not nearly as easy.

For what it’s worth the user manual calls MDS “Fuel Saver Technology” and the ECO light the “Fuel Saver Display”. It is mentioned on page 400 of the 2016 user manual.

I’ve got a 16 1500 Lone star.

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[Rampant]

I hear ya, and believe me, I know exactly when MDS is activated on mine. The easiest instance when the light will come on without MDS is when you’re cruising at about 35 and come to a stop light and let off the gas. You’ll notice the ECO light come on and your “current MPG” will go to 99. That’s not because MDS is active, but rather, fuel has been cut off from all injectors.

Uhh... If the fuel is cut off to all injectors, the engine will die. I don't think it will come on at speeds that low. When does the light shut off for you if it comes on at 35 and you are decelerating? Since putting 35s on, my MDS hardly comes on at all. If it does, it's more around the 45-55 range on decel. Can you make a video of what you're talking about? It sounds nothing like how mine acts.

Here is an excerpt from FCA about how the MDS works: "When MDS is operating, it is indicated by a “Fuel Saver” readout in the vehicles Electronic Vehicle Information Center." You can read the whole article here.

 

[Ratket]

My 2014 Ram 2500 6.4 -
Had no eco light.. “ my 2018 Ram 1500 does”
Mds would activate in tow haul- “ it was rare as hell”
Also the 5.7 in the 2500 didn’t have mds, I don’t know about 2018 and later.

With out tow haul on and letting the truck do it’s own thing, I had seen mds activate as low as 35 mph “was really really annoying”

Users report that wired up tuners show an increase in fuel flow to the 4 active injectors while mds is active by twice the amount when the motor is firing on all 8. Essentially using the same amount of fuel. < Now that is interesting.

 

[Will Ram 2500]

I hear ya, and believe me, I know exactly when MDS is activated on mine. The easiest instance when the light will come on without MDS is when you’re cruising at about 35 and come to a stop light and let off the gas. You’ll notice the ECO light come on and your “current MPG” will go to 99. That’s not because MDS is active, but rather, fuel has been cut off from all injectors.

MDS is coming on in that situation. I have dual exhaust and will see the light come on when slowing down like that and the exhaust sounds like crap as soon as the light comes on.