6.7L Cummins Common Problems and Fixes

The 6.7L Cummins in Ram heavy-duty trucks (2007.5-present) is a famously durable inline-six — the long block routinely goes high miles. Most of its headaches are around the emissions system and a few known components, not the core engine.

Emissions system: the usual suspects

The most common 6.7 Cummins complaints involve the aftertreatment:

• DPF clogging and frequent regens, especially on trucks that do short trips or heavy idling. Highway miles and correct oil keep it healthy.
• EGR cooler and valve carbon buildup and failures.
• NOx sensors and DEF system faults that can trigger derates.

None of these mean the engine is bad — they mean the emissions equipment needs upkeep and the truck needs to run hot enough to stay clean.

The CP4 pump (later years)

Ram moved to the Bosch CP4 high-pressure pump on certain later model years, carrying the same risk as other CP4 applications: a failure can contaminate the whole fuel system. Same insurance applies — keep fuel in it, use quality fuel, never run it dry, and consider a bypass kit.

Other known items

• Turbo (VGT) sticking — the variable-geometry turbo’s vanes can carbon up and stick, causing power loss or codes. Regular use and good maintenance help; severe cases need cleaning or replacement.
• “Death wobble” (front-end) on solid-axle trucks — a steering/suspension issue (track bar, ball joints) rather than engine, but a well-known Ram complaint.
• Lift pump / fuel delivery on some years.
• Grid heater bolt concerns discussed in enthusiast circles on certain years.

Maintenance that keeps it alive

• Oil changes on time with correct low-ash oil — Cummins blocks last forever if you do this.
• Fuel filters on schedule and water separator drained — protects injectors and the CP4.
• Give it highway runs so the DPF stays clean; don’t stack short trips.
• Don’t ignore emissions warnings — a NOx sensor is cheap; a derate on the interstate is not.

Buying used?

Check service records, scan for stored codes, look for emissions tampering/deletes (a red flag), and inspect the front end on solid-axle trucks. A maintained 6.7 Cummins is one of the most durable diesels on the road.

If your Cummins is regening constantly, throwing codes, or down on power, our shop can diagnose it and get it back to the durable workhorse it’s meant to be.