Freightliner DD13 DD15 Won't Accelerate Past 55 MPH (2024)

If your Freightliner DD13 DD15 won’t accelerate past 55MPH there may be a fewreasonsas towhyyou are experiencing thisissue.The reason whyFreightlinerputs you into an engine derate or reduces yourMPHisbecause they want you to correct the issue as soon as possible or damage may occur to your aftertreatment system.

Mainculpritfor this 55 MPH Speed Limit =Onsetofaftertreatmentproblems

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%LowPower 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 causea 55MPH 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 pumpfails,then you must replace it for the system to work properly.
• NOxSensor 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 causescommunicationerrorsbetween CPC & MCM & ACM.
• AftertreatmentHarnessRubbedThrough - This can cause random faults in your emission system.
• Aftertreatment systemneeds 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 andemissions

• 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.
• MCMcontrols and regulates all your fuel, timing,EGRand emission components.
• Source 00 or EEC 00 (faultcode 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 sourceaddress,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 1231Fail 9- ACM Not communicating with your MCM / CPC
• EEC61SPN 1231Fail 9-ACM Not communicating with your MCM / CPC
• EEC61SPN 625Fail 9-ACM Not communicating with your MCM / CPC
• EEC 61 SPN 4364Fail1-Selective Catalyst ReductionNoxConversion Very Low
• EEC 61 SPN 4364 Fail18-Selective Catalyst ReductionNoxConversion LOW
• EEC 61 SPN 3364 Fail2-Improper DEF Quality
• Any otherAftertreamentfault codestied to DEF
• NOx Conversion fault codes -More details in this blogpost 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 2017or newerFreightliner orWesternStartruckone of thefault codes belowmay be tied to your derate issue.You should also make sure that your software is up to date on your engine and aftertreatmentcomputers because the fault codes can also appear if your software is not updated.

If thefollowingfault codes do not clear after youhavevalidatedthatthe problemhas beencorrected,then you may need to replaceyour MCM.We have seeninstanceswhere these fault codes latch on and replacement of the MCM is necessary.

• EEC 0 SPN 521049 FMI 31
• DEF Inducement CEL Lamp Active
• Thisfault codesetswhenthere is acodepresent 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,vehiclespeedlimited to55MPHdue to power derate
• Dash Lamps
• DEFlamp is on
• Verification
• Parked SCRefficiencytest forextended SCRfaults
• Highidleregeneration for DPF and NOxfaults
• Forced DPFregen
• EEC 0 SPN 521050 FMI 31-MCM (Motor Control Module)
• DEF InducementCEL Lamp Active
• Thisfault codeappearsafter SPN 521049/FMI 31 and thespeedlimit has beenreduced to55 MPH(90KPH)
• Monitored Parameters
• SCR and Diesel Particulate Filter (DPF)sensors
• Engine Reaction
• 40% Derate, Vehiclespeedlimited to 5MPH(8KPH).
• Dash Lamps
• Checkenginelight(CEL)on
• Verification
• Parked SCRefficiencytest forextended SCRfaults
• High Idleregeneration for DPF and NOxfaults
• Forced DPFregen

• EEC 0 SPN 521052FMI 31
• DEF Inducement CEL Lamp Active
• Thisfault codesetsafter SPN 521049/FMI 31 and thespeedlimit has beenreduced to 55 mph(90 KPH).
• Monitored Parameters
• SCR and Diesel Particulate Filter (DPF)sensors
• Engine Reaction
• 40% Derate, Vehiclespeedlimited to 5MPH(8KPH).
• Dash Lamps
• Check Engine Light(CEL)on
• Verification
• Parked SCRefficiencytest forextended SCRfaults
• Highidleregeneration for DPF and NOxfaults
• Forced DPFregen

Whatcan you do? (DIY)

• Check your DEF fluid
• Make surethatit’s topped off
• Look up the fault code that is on your dashboard
• If you don’t have a way to look up a faultcode,you may need an additional diagnostic tool such as OTR Diagnostics to pull this fault codefrom your truck
• Clear the fault codes
• You clear the codeswith a dealer level servicetool,oryou can useOTR Diagnostics to perform the resets.
• Perform a forcedDPF service regen
• When you perform aforced DPFregen 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 afew fault codes that require you to run a forcedDPF regentoverifythat the system is working
• We have seen a fewscenario'swhere resetting the fault codes and performing a forced DPF regen will clearthese ghost codes that hinder your truck from going over 55 MPH

Helpful Videos

FixingDEF 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.

Looking to learn more? Check out our other blog posts.

• How long should a forced DPF regeneration last?
• Tell-tale symptoms of a successful (or unsuccessful) forced DPF regeneration.
• What is face plugging? How does it happen? How can I fix it?
• What happens if your truck can no longer regen?
• What is Forced DPF Regen?
• Common DPF questions Answered!
• What does poor DEF quality Mean?

OTR Diagnostics allows you to read and reset fault codes, view live data, and run advanced diagnostic functions, including forced DPF regen with your mobile phone or tablet.

• Shop OTR Diagnostics | Professional (All-in-One) Engines