The number one cause of a 5 MPH derate in a Volvo truck is the SCR/DEF system not operating properly. The SCR/DEF system was implemented in Volvo Trucks 2011+ to curb exhaust emissions on Class 8 trucks.
If you have a Paccar engine and are stuck in 5 MPH derate check out this blog post.
What is a derate?
A derate means that the program inside the engine computer limits either the power or vehicle speed. A derate is designed to protect you from causing engine or DPF damage. A derate can be caused by various sensors or system. However, when it’s a specific 5 MPH derate then you can be certain that the problem is related to the emissions, aka the aftertreatment system.
What components make up the emission system that control the 5 MPH derate?
- DEF Fluid – The tank with the Blue Cap holds DEF Fluid. This has a level sensor and a quality sensor to make sure the concentrations are in allowable limits. If you have bad DEF fluid, this can cause DEF quality issues and can put you into a derate.
- DEF Doser Valve – Regulates the injection of the DEF fluid into your SCR Catalyst.
- DEF Pump Assembly – The heart of your DEF system that pumps the DEF fluid throughout the system. If this fails you will go into a derate immediately
- NOx Sensors, both inlet and outlet sensors – When the sensor detects much NOx in the exhaust stream, it tells the SCR/DEF system to inject more urea, which uses ammonia to reduce emissions levels in your system.
- ACM – Aftertreatment Control Module – This module controls the operation of the emission system. The ACM and Engine Control Module (ECM) are in direct communication to make sure the system is operational. This also regulates your DPF system and all the sensors associated with that system.
The dreaded fault code that causes the 5 MPH derate!
This fault is related to the “SCR Inducement” which is what regulates your truck to this derate.
2011-2013 EPA10 Trucks
- SPN 5246 FMI 0 – SCR Inducement Final Level - Causes 5 MPH Derate
2014-2019 GHG14, GHG17 Trucks
- DEF SCR Inducement Faults
How to temporarily override this 5 MPH derate on a Volvo?
Some Volvos will allow you to temporarily override the derate if you unplug the speed sensor on the transmission. This sensor is either located at the tail shaft of the transmission or if it’s an I-Shift on the right side of the rear transmission. This will eliminate your vehicle speed from displaying on the dashboard once disconnected. This will also limit your RPM to ~1400 RPM so you won’t have full power and you will have to change your gears manually because the transmission won’t know the speed. We do not endorse this method, but it’s good to know in case of an emergency. Beware some trucks, even if disconnected, will not go over 5 MPH – it is programmed even if the speed sensor is disconnected, so this method may not work all the time.
How to fix this 5 MPH derate?
You need to see what caused the “SCR Inducement Code” to come up in the first place. A failed component is usually what triggers this code.
- Failed DEF Doser valve, SPN 5394
- Run out of DEF fluid, SPN 5392, SPN 1761
- Inlet & Outlet Nox Sensor Failed, SPN 4094
- EGR System Malfunction causing Nox Efficiency problems
- DEF Pump Failed, not making pressure, SPN 4334, SPN 4339
- ACM Failed – Harness failure – No Power to ACM causes DEF gauge to be empty and showing Datalink error and SCR Malfunction. The ACM / ECM could also need updating to eliminate ghost issues.
Can you do updates to the emission system?
The short answer is yes, updates are recommended if they are available. It’s recommended to see if you have any updates available and to do them if so because this can remove any bugs or issues. However, please note that this isn’t a fix for all your problems or ghost codes, but it’s good practice to have the latest updates.
Let us know in the comments of any helpful tips and things you do to keep your system operational.
Until next time 👋