Freightliner DD13 DD15 Won't Accelerate Past 55 MPH

If your Freightliner DD13 DD15 won’t accelerate past 55 MPH there may be a few reasons as to why you are experiencing this issue. The reason why Freightliner puts you into an engine derate or reduces your MPH is because they want you to correct the issue as soon as possible or damage may occur to your aftertreatment system.  

Main culprit for this 55 MPH Speed Limit = Onset of aftertreatment problems  

When you are limited 55 MPH you can be confident that it is most likely due to your aftertreatment system.   

• Symptoms 
• DEF Light Flashing (RED)  
• DEF Gauge Empty (Possible) 
• 25% Low Power that limits you to only go 55 MPH 
• Once this happens you are racing against time before your truck limits you to 5 MPH  

• Causes 
• Components that can cause a 55 MPH derate  
• DEF Fluid Ran out - (Empty tank) - Refill as soon as possible.  
• DEF Pump Failure - This is the heart of your system that pumps DEF fluid into the 1box. If this pump fails, then you must replace it for the system to work properly.  
• NOx Sensor Failure - NOx Inlet and NOx Outlet sensors are located on your 1box. These sensors measure how efficient your emission system is and will cause a derate condition if they are faulty or have incorrect readings.  
• ACM (Aftertreatment Control module) Not Powered - This causes communication errors between CPC & MCM & ACM.  
• Aftertreatment Harness Rubbed Through - This can cause random faults in your emission system.  
• Aftertreatment system needs to be updated by the manufacturer. 
• Ensure your software program is up to date.  

Engines that are affected 

• Detroit Diesel DD15  
• Detroit Diesel DD13 

Years and emissions 

• 2011 - 2021 Year model 
• EPA10 
• GHG14  
• GHG17  

Models that are affected 

• Freightliner Trucks - All models that use this engine 
• Freightliner Cascadia (Most Popular) 
• Western Star - All models that use this engine 

Terms to know  

• SA (Source Address) 
• Relays information on which module is generating the fault code you have. 

• MCM (Motor Control Module)  
• This is one of the most important components to your engine. Without this module your engine will not start.  
• MCM controls and regulates all your fuel, timing, EGR and emission components.  
• Source 00 or EEC 00 (fault code detail) 
• Located on your engine. 

• CPC (Common Powertrain Module)  
• This module will regulate certain parameters with your vehicle’s speed and your cruise control.  
• CPC ties the MCM to your aftertreatment computers through a proprietary datalink.  
• Source 1 or EEC 01 (fault code detail) 
• Located inside dash panel inside the cab. 

 

• ACM (Aftertreatment Control Module)  
• This module controls your DPF and your DEF systems.  
• ACM regulates all the fault codes that are tied to your aftertreatment system. If you have any fault codes coming from this source address, then it is relaying information directly to your dashboard or your diagnostic scan tool.  
• Source 61 or EEC 61 (fault code detail) 
• Located on your aftertreatment 1box. 

What fault codes will trigger this derate?  

If you drive with the following fault codes, you may enter a 5 MPH derate 

• ENG 1 SPN 1231 Fail 9 - ACM Not communicating with your MCM / CPC 
• EEC 61 SPN 1231 Fail 9 - ACM Not communicating with your MCM / CPC 
• EEC 61 SPN 625 Fail 9 - ACM Not communicating with your MCM / CPC 
• EEC 61 SPN 4364 Fail 1 - Selective Catalyst Reduction Nox Conversion Very Low 
• EEC 61 SPN 4364 Fail 18 - Selective Catalyst Reduction Nox Conversion LOW 
• EEC 61 SPN 3364 Fail 2 - Improper DEF Quality 
• Any other Aftertreament fault codes tied to DEF 
• NOx Conversion fault codes -  More details in this blog post about SCR NOx efficiency problems.

   *Seek out a repair facility who can help you in the case you are limited to 5MPH.

2017+ Trucks - GHG17  

If you have a 2017 or newer Freightliner or Western Star truck one of the fault codes below may be tied to your derate issue. You should also make sure that your software is up to date on your engine and aftertreatment computers because the fault codes can also appear if your software is not updated.  

If the following fault codes do not clear after you have validated that the problem has been corrected, then you may need to replace your MCM. We have seen instances where these fault codes latch on and replacement of the MCM is necessary.  

• EEC 0 SPN 521049 FMI 31 
• DEF Inducement CEL Lamp Active 
• This fault code sets when there is a code present for the following:  
• Diesel Exhaust Fluid (DEF) Tank Level 
• DEF Dosing Unit 
• DEF Pump 
• NOx Sensors 
• Blocked DEF Line 
• DEF Quality 
• NOx Efficiency 
• Selective Catalyst Reduction (SCR) Harness 
• SCR Sensor 
• Monitored Parameters 
• SCR and Diesel Particulate Filter (DPF) Sensors 
• Engine Reaction 
• 25% Derate, vehicle speed limited to 55 MPH due to power derate 
• Dash Lamps 
• DEF lamp is on 
• Verification 
• Parked SCR efficiency test for extended SCR faults  
• High idle regeneration for DPF and NOx faults 
• Forced DPF regen 
  
  
• EEC 0 SPN 521050 FMI 31 - MCM (Motor Control Module)  
• DEF Inducement CEL Lamp Active 
• This fault code appears after SPN 521049/FMI 31 and the speed limit has been reduced to 55 MPH (90 KPH)  
• Monitored Parameters 
• SCR and Diesel Particulate Filter (DPF) sensors 
• Engine Reaction 
• 40% Derate, Vehicle speed limited to 5 MPH (8 KPH).  
• Dash Lamps 
• Check engine light (CEL) on  
• Verification 
• Parked SCR efficiency test for extended SCR faults  
• High Idle regeneration for DPF and NOx faults 
• Forced DPF regen 

• EEC 0 SPN 521052 FMI 31 
• DEF Inducement CEL Lamp Active 
• This fault code sets after SPN 521049/FMI 31 and the speed limit has been reduced to 55 mph (90 KPH). 
• Monitored Parameters 
• SCR and Diesel Particulate Filter (DPF) sensors 
• Engine Reaction 
• 40% Derate, Vehicle speed limited to 5 MPH (8 KPH).  
• Dash Lamps 
• Check Engine Light (CEL) on  
• Verification 
• Parked SCR efficiency test for extended SCR faults  
• High idle regeneration for DPF and NOx faults 
• Forced DPF regen 

What can you do? (DIY) 

• Check your DEF fluid  
• Make sure that it’s topped off
• Look up the fault code that is on your dashboard 
• If you don’t have a way to look up a fault code, you may need an additional diagnostic tool such as OTR Diagnostics to pull this fault code from your truck
• Clear the fault codes  
• You clear the codes with a dealer level service tool, or you can use OTR Diagnostics to perform the resets.  
• Perform a forced DPF service regen 
• When you perform a forced DPF regen on your truck it checks all the sub-systems that are in place to make sure that everything is working properly
• You can perform a forced DPF regen with a dealer level service tool, or you can use OTR Diagnostics .
• There are quite a few fault codes that require you to run a forced DPF regen to verify that the system is working
• We have seen a few scenario's where resetting the fault codes and performing a forced DPF regen will clear these ghost codes that hinder your truck from going over 55 MPH 

Helpful Videos  

Fixing DEF Quality Fault Codes  

• https://www.youtube.com/watch?v=zr5em086Tv4 
• https://www.youtube.com/watch?v=esuK3chswRc 

We hope you find this blog post useful if you are stuck in a derate or if you are just looking to educate yourself in the case that you find yourself stuck in a derate.

Until next time 👋
Stay safe, stay healthy, & God bless.