2019-2023 Ram 1500 ATMM: Fixing the 5.7L HEMI MDS Vibration and Drone
A deep dive into diagnosing and replacing the Active Tuned Mass Modules that cause annoying vibrations when the 'ECO' light comes on.
- The ATMM's sole purpose is to cancel out vibration from the 5.7L HEMI's fuel-saving MDS (ECO mode).
- Failure symptoms are very specific: a drone/vibration ONLY when the ECO light is on, or a 'Service ATMM' message on the dash.
- There are two different modules: a left (driver) and a right (passenger) side. They are not interchangeable.
- When buying a used module, the most important check is for cracks in the plastic housing near the electrical connector, as this is a common failure point.
What Are the Symptoms of a Failing ATMM?
When an Active Tuned Mass Module begins to fail, the symptoms are usually very distinct and tied to the engine's MDS operation. You may notice one or more of the following signs:
- Vibration or Drone When in ECO Mode: The most common symptom is a new or worsening vibration, drone, or 'booming' sound felt in the floor, steering wheel, or seats. This typically occurs at low, steady RPMs (around 1200-1500) or at highway speeds between 45-65 mph when the truck is in ECO mode (MDS active). The vibration will immediately stop if you accelerate, manually select a gear, or engage Tow/Haul mode, as these actions disable MDS.
- Dash Warning Messages: The instrument cluster may display a message like "Active Tuned Mass Module Temporarily Unavailable" or "Service Active Tuned Mass Module". In some cases, this warning may be accompanied by a persistent and highly distracting chime that repeats every few seconds.
- Diagnostic Trouble Codes (DTCs): A professional scan tool may reveal stored trouble codes. A common code pointing to a faulty passenger side module is C1517 - Right Vibration Sensor Circuit Short to Ground.
Known Issues and Diagnostic Tips
While the module itself can fail internally, forum discussions with owners have highlighted a few common issues to check first:
- Cracked Housing: Many owners have discovered that the plastic housing of the ATMM, particularly around the electrical connector, can crack. This allows water to get inside, shorting out the electronics and causing the "Temporarily Unavailable" message, especially after rain or a car wash.
- Low Battery Voltage: A weak or dying battery can cause a flood of low-voltage error codes across various vehicle modules, including the ATMMs. If you see the service message shortly after jump-starting the truck or replacing the battery, the error may simply need to be cleared by a dealer or with a capable scan tool.
- Related Vibration TSBs: Not all vibrations are caused by the ATMM. Owners have reported other issues that can be confused with a bad module. One is addressed by TSB 23-023-19, which involves a software reflash for the Active Noise Cancellation (ANC) system to fix a drone. 🎬 Watch: How to fix the ANC system's loud engine hum. Another unrelated TSB involves adding a small steel plate to the truck bed, which owners report is ineffective for this type of vibration.
Pro Tip: If you are experiencing the constant chiming from the "Temporarily Unavailable" message, you can unplug the electrical connector on the faulty module as a temporary fix to stop the noise. The truck is perfectly safe to drive without it, but the MDS drone will be noticeable until the part is replaced.
Buying a Used Active Tuned Mass Module: What to Check
Since new aftermarket versions of this electronic module are not commonly available, a quality used OEM part is often the most cost-effective solution. Here’s what to look for when buying a recycled ATMM.
1. Physical Inspection
- Inspect the Connector Housing: This is the most critical check. Carefully examine the area where the wiring harness plugs in. Look for any hairline cracks in the plastic, as this is a known failure point that leads to water damage. Reject any module with visible cracks.
- Check the Mounts: The module is attached to the frame with integrated rubber bushings. Ensure these bushings are not torn, dry-rotted, or soaked in oil. Damaged mounts can prevent the module from working effectively.
- Look for Impact Damage: Since these are mounted on the frame rails, they can be damaged in side impacts or from road debris. Avoid any units with dented canisters or bent mounting brackets.
2. Compatibility Verification
Warning: The driver and passenger side modules are different parts and are not interchangeable. They have unique part numbers.
Always verify the part number before purchasing. The number is typically printed on a sticker on the module itself. While part numbers can be superseded, here are the most common ones:
- Right (Passenger Side) ATMM: 68356654AD. This number replaces older versions 68356654AB and 68290378AB.
- Left (Driver Side) ATMM: 68356653AD. This number replaces older versions 68356653AB and 68356653AC.
These modules are specific to the 5th Generation (DT) Ram 1500 (2019 and newer) and will not fit Ram 1500 Classic (DS) models.
Replacement Cost Comparison
The cost to replace an ATMM can vary, but buying a used OEM part can offer significant savings over a new part from the dealer.
| Part Source | Estimated Cost |
|---|---|
| New OEM | $330 - $510 |
| New Aftermarket | Not commonly available |
| Used OEM | $100 - $250 |
| Shop Labor | $150 - $250 |
Frequently Asked Questions (FAQ)
Do I need to replace both ATMMs at the same time?
No. The left and right modules operate independently. You only need to replace the one that has failed. A proper diagnosis or trouble code can help identify which side is faulty.
Is any special programming needed after installation?
No, these modules are typically plug-and-play and do not require programming. However, if a trouble code was stored in the vehicle's computer, it may need to be cleared using a scan tool after the new part is installed.
Can I just disable the MDS system instead of replacing the ATMM?
Yes, you can prevent the vibration by using the gear limit buttons on the steering wheel to lock out the highest gears or by driving in Tow/Haul mode, both of which disable MDS. However, this will negatively impact your fuel economy. Replacing the faulty ATMM is the correct repair to restore both ride quality and fuel efficiency.
Could my vibration be something else?
Absolutely. While a faulty ATMM is a common cause, vibrations can also come from unbalanced tires, a bad driveshaft, or exhaust issues. The key indicator for an ATMM problem is that the vibration is almost exclusively present when the 'ECO' light is on and disappears the moment it turns off.
Helpful Videos
Technical Specifications
OEM Part Numbers: Right/Passenger Side: 68356654AD, 68356654AB, 68290378AB Left/Driver Side: 68356653AD, 68356653AC, 68356653AB
Electronically controlled vibration-canceling damper. Two required per vehicle (left and right).
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
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