| Engine | Ram model years | What it means for owners |
|---|---|---|
| 5.9 12-valve | 1989 to mid-1998 | Mechanical Bosch injection pump; no engine computer running the fuel system. |
| 5.9 24-valve (ISB) | mid-1998 to 2002 | Electronic Bosch VP44 injection pump fed by an in-tank or frame-mounted lift pump. |
| 5.9 common rail | 2003 to 2007 | High-pressure common-rail injection with electronic injectors. |
| 6.7 Cummins | mid-2007 on | Common rail plus diesel particulate filter; later trucks add DEF (urea) aftertreatment. |
Years from Cummins, MotorTrend and DieselHub. Changeover years were split mid-year; confirm with your engine dataplate and VIN.
What makes it different
The 6.7 kept common-rail injection and added a diesel particulate filter (DPF) from the start. Later trucks also use selective catalytic reduction with diesel exhaust fluid (DEF): Cummins' maintenance guide adds a DEF filter to the schedule for those engines.
Living with the emissions system
- Let regenerations finish when you can. Lots of short trips and idling make it harder for the DPF to clean itself.
- Use only certified DEF, keep the cap tight, and keep it clean. See air and DEF.
- Removing or defeating emissions parts is illegal on road vehicles under the Clean Air Act. See first mods and what to avoid.
Valve lash on newer trucks
Cummins says the 2019 and later chassis-cab 6.7 uses hydraulic lash adjusters, which eliminate the overhead adjustment. Older 6.7 engines are adjustable. See valve lash.
Chassis by year
6.7 trucks span three chassis layouts: 3rd gen (to 2009), 4th gen (2010 to 2012) and the radius-arm trucks from 2013/2014. Shop 3rd gen, 4th gen or 5th gen parts. Radius-arm owners often start with the adjustable track bar for 2014-2018 and the 4.5 and 5th gen steering linkage.
Where this comes from
- Cummins: Follow the liter, evolution of the 5.9L to the 6.7L pickup engine
- MotorTrend: 5.9-liter Cummins history and specs
- DieselHub: 5.9L and 6.7L Cummins FAQ
- Cummins: Motorhome quick reference guide, B6.7 / ISB (PDF)
- Cummins: 6.7L Turbo Diesel for 2019 Ram chassis cab
- U.S. EPA: Diesel particulate filter (DPF) technical bulletin
- Cummins: DEF quality and maintenance (PDF)
- U.S. EPA: Tampering and aftermarket defeat device enforcement policy
Last reviewed 2026-10-19. General information only: your owner's manual and service information come first.