Introduction to Automatic “Auto Desorb“ Feature on MX Powered Peterbilt Chassis

By Allstate Peterbilt Group | Posted in Diesel Technicians & Mechanics on Monday, July 15th, 2019 at 7:29 pm

When Engine software version RC 7 was released in 2018, it added a whole new level of functionality to the MX powered Peterbilt chassis. Continue reading to learn about Automatic regens, or “Auto Desorb,” and how it can benefit you and your vehicle. .

What Is Automatic Regens?

Automatic regens is also known as Auto Desorb, and it’s a feature that gives your truck the ability to perform small maintenance regenerations on its own. In other words, it doesn’t require a driver’s interaction to perform regen functions. 

Basically, these automatic mini regens help reduce the burden on the truck driver when it comes to performing mandatory stationary regens. And this can be particularly helpful to those who operate trucks that are older, as well as to those who drive in cold climates and who idle for more than three hours continuously.  

What Are the Benefits You Can Derive from a Truck with Automatic Regens?

What’s the benefit that you can derive from Auto Desorb? Put simply, it means that you won’t have to put your truck out of service for upwards of an hour, wasting precious time. And it also means you don’t need to initiate these types of regens yourself. 

By using this attractive new feature on your Peterbilt, you can:

  • Prevent shortened aftertreatment life
  • Reduce costly downtime
  • Avoid nuisance manual regens

Some Information on the Automatic Diesel Particulate Filter (DPF) 

With Automatic DPF, warm-up may happen automatically, without you needing to provide any input, while your truck is idling. Also, if you’re idling for extended stretches of time, the truck will increase engine speed periodically, sometimes without notifying you, so it can reduce the need to do a parked regeneration. 

In the event that a parked regen is required, you won’t be able to drive, but the truck will be safe to drive during a DPF Warm-Up. You can also stop the Automatic DPF Warm-up by pressing the brake. But if you stop the Warm-up, a 10-minute restart delay timer will begin, and the truck will attempt this function every 10 minutes until it can be completed. 

Can you disable this functionality if you want to? Yes, but then you might need to do a parked regen, especially if your truck has experienced extended idling. 

How to Regenerate Peterbilt Trucks  

Here’s what to expect when you use Automatic DPF Warm-up:

  • It will occur every 3 to 8 hours if you’re idling for extended periods of time.
  • It will take anywhere from 20 minutes to 1 hour to complete.
  • If your notifications are available, you’ll see a 2-minute timer that will serve as a countdown that will let you know that the Auto DPF Warm-up is going to begin.
  • The engine speed will be elevated while the Warm-up is happening. However, it won’t change engine speed if PTO is active. For Auto DPF Warm-up to occur with PTO active, PTO Engine Speed would have to be above roughly 900 rpm. 

Operator Actions That Will Activate or Deactivate Auto Desorb

To activate auto desorb:
  • Accelerator pedal not pressed
  • Foot brake not pressed
  • Clutch pedal not pressed
  • Parking brake set
  • DPF regen switch isn’t set to “inhibit”
  • Truck in neutral and speed is 0
  • Coolant at operating temperature
  • There aren’t any related engine or aftertreatment faults
  • If PTO is active, engine speed is greater than 900 rpm (engine speed threshold varies based on ambient conditions)
  • Engine load is less than 600 lb-ft (engine load threshold varies based on engine speed)

To deactivate auto desorb:

  • Accelerator pedal pressed
  • Foot brake pressed
  • Clutch pressed
  • Parking brake not set
  • DPF regen switch is set to “inhibit”
  • Truck speed is over 0
  • Coolant isn’t at operating temperature
  • There are related engine or aftertreatment faults (for example: BPV, VGT, EAS overtemps, pre-DOC temp, etc.) 
  • If PTO is active, engine speed is less than 900 rpm (engine speed threshold varies based on ambient conditions)
  • Engine load is greater than 600 lb-ft (engine load threshold varies based on engine speed)

What Truck Models Have Automatic DPF Warm-up?

If you’re driving a MY17 truck, the software can be updated to MY17 RC7. This will enable Automatic DPF Warm-up Functionality. Keep in mind that the functionality will be disabled by default. 

If you’re operating a MY18 truck, the software can be updated to MY18 RC2. This will enable Automatic DPF Warm-up Functionality. Bear in mind that the functionality will be disabled by default on a chassis that was built prior to May 1, 2018, and it will be enabled by default on trucks that were built after May 1, 2018. 

Additional Helpful Information About Your Diesel Particulate Filter (DPF)

You’ll know that your DPF is regenerating because the engine RPM will increase. This will be done to create higher exhaust temperatures to help with the regen. However, you can also look for a “high exhaust temperature” warning when your park brakes are set and your truck is doing a regen. 

The average DPF filter might need to be cleaned around 250,000 miles. And it might need to be replaced around 500,000 miles, as a couple of rough estimates. Remember: high idle times are the biggest contributor to premature cleanings and failures of your DPF. And you’ll be able to tell if your DPF is clogged by looking for fault codes, such as “DPF differential pressure high.” 

We hope that this information clears up what the Auto Desorb feature is, and why it’s so popular. Be sure to take advantage of it on your Peterbilt chassis if you can!


Updated on November 20, 2020

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