DEF Software Update

PACCAR and Cummins recently released new software updates that improve how trucks respond to certain DEF-related faults. The updates will increase uptime and allow trucks more time on the road to find a repair shop to stop at when DEF system issues arise. We understand that many people may have questions about how these updates will affect their fleet, so below we have provided the answers to some frequently asked questions for you.

FAQS

Does this mean I don’t need DEF anymore?
No. DEF is still required for proper engine operation. 

Are DEF derates gone?
No. Certain DEF-related derates have been modified. Other derates still exist. 

Will my truck still derate?
Yes. Depending on the fault, your truck may still reduce power or vehicle speed. 

What's different?
Instead of reaching a 5 MPH derate in about four engine hours for certain DEF-related faults, many updated trucks now allow approximately 160 engine hours before reaching a 25 MPH final inducement. 

Does this apply to every fault code?
No. Only specific DEF-related inducement logic has changed. Other engine protection strategies remain unchanged. 

Can I ignore DEF warning lights now?
No. The update provides more time, not permission to continue operating indefinitely with an active fault. Repairs should still be completed promptly. 

Does my truck still require DEF?
Yes. Every truck still requires DEF. 

Is this update free?
No. This is an optional customer-pay software update and is not a warranty campaign. 

Will this affect my warranty?
No. However, failures caused by not using DEF or by tampering with the emissions system may still not be covered under warranty. 

Which trucks are eligible?
Eligibility depends on engine family, model year, and software availability. Your local Rihm Kenworth service department can verify whether your truck qualifies. 

Still have more questions?
Please reach out to your local Rihm Kenworth service department to get them answered.