6.7 Cummins common problems and what to watch for
The Cummins 6.7L inline-six in Ram Heavy Duty pickups has a strong reputation for its bottom end and longevity. Most of the trouble on these engines lives in the emissions, air and fuel systems around it. Here are the issues that come up most often, grouped by era.
Engine eras
| Years (Ram HD) | Key changes |
|---|---|
| 2007.5-2012 | First 6.7: DPF, EGR, VGT turbo. No DEF on most pickups. |
| 2013-2018 | DEF/SCR added on pickups. Revised turbo and emissions hardware. |
| 2019-2026 | Major redesign: compacted graphite iron block, new fuel system and turbo, higher output versions. |
Exact details vary by model year and by Ram 2500 vs 3500 vs cab-and-chassis. Always check recalls and service bulletins for the VIN.
EGR, VGT and soot
- VGT turbo sticking. Soot on the vane ring causes sluggish boost or overboost codes. Common on trucks that idle a lot. Often fixed by cleaning; actuator replacement in some cases. See diesel turbo symptoms.
- EGR valve and cooler. Sticking valves and cooler leaks show up on higher-mileage trucks. See EGR cooler failure symptoms.
- DPF loading and regens on 2007.5-2012 trucks especially, which had frequent regen complaints. See DPF regeneration.
Grid heater
Cummins uses an intake grid heater instead of glow plugs. The heater, its relays and its wiring can fail, causing hard cold starts and white smoke. There have also been concerns about grid heater bolts or the element breaking on some years; a broken element entering the engine is a serious failure, which is why some owners check or update it. See cold-start heating systems.
DEF and NOx (2013+)
- NOx sensor failures, upstream and downstream, are a frequent repair. See bad NOx sensor symptoms.
- DEF heater and DEF pump/doser faults, sometimes with derate warnings (P20EE, P20B9).
- Software updates have addressed several false SCR codes.
Fuel system
Fuel quality matters on every common-rail engine. Watch for low rail pressure codes (P0087), water-in-fuel warnings and lift pump failures. Keep up with fuel filter changes. See fuel filter replacement.
Checks when buying a used 6.7 Cummins
- Scan for stored and pending codes, including emissions and DEF codes.
- Ask for service records: oil, fuel filters, coolant.
- Check for blue smoke, black smoke or coolant loss.
- Check the turbo responds smoothly with no overboost or underboost codes on a test drive.
- Run a VIN check for open recalls and emissions warranty status.
- Look for signs of tuning or emissions deletes. A deleted truck is illegal to drive on public roads and can be very expensive to return to stock.
Related trouble codes
FAQ
What year 6.7 Cummins is the most reliable?
Opinions vary. Many owners like 2013 and later trucks for improved emissions hardware, and the 2019+ redesign brought further changes. Condition and maintenance history matter more than the year.
Does the 6.7 Cummins have glow plugs?
No. It uses an intake air grid heater to help cold starts.
How many miles can a 6.7 Cummins last?
Well-maintained 6.7 Cummins engines regularly pass 300,000 miles. Emissions and fuel system parts usually need attention well before the core engine.
What is the most common 6.7 Cummins problem?
Emissions-related issues: sticking VGT turbos, EGR problems, DPF loading, and on 2013+ trucks NOx sensors and DEF system faults.
More diesel guides
General guidance only. Check the service information, recalls and bulletins for your exact vehicle. Costs are rough 2026 US estimates, not quotes. Need a number for your truck? Try the repair cost estimator.