What Is MDS? How Do I Disable It on My Hemi Engine?

If you own a Dodge or Ram truck with a Hemi engine, it might have an MDS system. This guide and video explains what Chrysler’s MDS system is and how to temporarily disable it on the Hemi in your vehicle.

How to Temporarily Disable Your Hemi’s MDS

What Is MDS?

MDS stands for multi-displacement system. MDS helps improve fuel economy and it reduces the amount of emissions. Since V8 engines can use a lot of power and gas, MDS turns off 4 of the 8 cylinders by shutting down the fuel injectors and collapses the valves for the intake and exhaust with solenoids.

Why Turn Off MDS? Can I Permanently Disable It?

The MDS will be in a truck like a Ram with a Hemi for better fuel economy. Disabling the MDS can give you full engine power (maximum horsepower and torque) if you need it.

If you want to permanently disable the MDS, buy a tuner. Otherwise it will take a few seconds to temporarily disable it.

How to Temporarily Disable MDS on My Hemi

Some say pressing the tow/haul button will deactivate the MDS, but this will only work with 6-speed transmissions. With the 8-speed transmissions, this button will just change some shift patterns in the transmission.

Tow/haul button on a Ram truck

Time needed: 10 minutes.

Steps to Disable MDS on a Hemi

  1. Find Your Shifter

    The process is quick and easy but is different depending on the kind of shifter and transmission you have.

  2. For Shifters in the Center of the Vehicle, Put the Shifter in Manual Mode and Shift It to the Driver Side 6 Times

    The 2013 Ram with a 5.7L Hemi in this example has a 6-speed transmission with a shifter like the one pictured below.

    During your drive, bring the shifter all the way to the bottom and pull to the driver side and release, which puts the vehicle in manual mode.

    Then pull the shifter to the driver side and release 6 times. The number 6 should appear on the dash.

  3. For Knob Shifters, Push the Down Button on the Steering Wheel to Engage Manual Mode and Press the Up Button to Match the Gears of Your Transmission

    Some vehicles have a knob next to the center console instead of a shift-stick.

    If you have a knob shifter, press the down button on the steering wheel, which engages manual mode. Then continue by pressing up until you reach the maximum amount of gears that your vehicle has.

  4. For Column Shifters on the Steering Wheel Column, Press the Down Button to Engage Manual Mode and Press the Up Button to Match the Gears of Your Transmission

    If you have a column shifter on the steering wheel column, the end of the shifter will have buttons.

    While in Drive, press the down button, which will put the transmission into shift for you, and then press the up button until the maximum shift range number appears on the dash.

Once the gauge cluster is set to the maximum number of gears you can use, continue driving and you’ll notice the MDS system is not turning on. This means you will be on all cylinders for maximum horsepower and torque.

Scan tool reading a disabled MDS system on a 2013 Ram truck with a 5.7L Hemi

Are the MDS and Eco-Light Part of the Same System?

You may notice the MDS and eco-light activating and deactivating at the same time, but these are two separate systems.

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What Is MDS? How Do I Disable It on My Hemi Engine? - 1A Auto
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What Is MDS? How Do I Disable It on My Hemi Engine? - 1A Auto
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Learn what Chrysler's multi-displacement system (MDS) is and how to disable it. Expert mechanics in this article and video explain how to disable MDS on your Hemi quick and easy
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1A Auto
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