The Lemon Index
The 5.9 L inline-6 turbo diesel in the Ram 2500/3500 (Heavy Duty), model years 1999–2007. Owners filed 3,245 complaints about trucks with it (matched by VIN); 4% name the engine, #12 of the 12 diesel truck engine generations we track (1 = the most).
Known issues, checked against owner complaints
Problems owners of trucks with this engine name much more often than owners of other diesel truck generations (at least 1.5× the median, and 10+ complaints):
- Injectors. 81 of 3,245 owner complaints (2.5%) mention an injector, against a median of 1.2% for the other diesel truck generations we track.
2007 dodge diesel 3500 truck fuel filter system doesn't work will not stop any thing and kills injectors.
2007 owner · NHTSA complaint 10294487
Also often talked about, but not standing out in complaints to NHTSA: stalling and power loss (lift pump, VP44 pump on 1999–2002) (163 of 3,245, 5.0%, peers 7.8%). That doesn't mean it never happens, only that owners rarely file it with the government.
What YouTube owners say Tone 0-100, higher = more praise than trouble.
Average owner tone 38/100 across 9 model years, from 175 videos about this engine and its cars.
Most-watched videos
- We Double the Horsepower of a 24 Valve Cummins 1,134,114 views
- LOCKED UP 5.9 24V Cummins Diesel Teardown. So You CAN Kill a 5.9... 932,080 views
- Double The Horsepower 12 Valve Cummins 691,099 views
Counted from video titles and captions: praise words against trouble words, weighted by views. Videos only count when the title names this engine or a car that had only this engine in those years.
Owner complaints by model year
Counts of complaints filed so far. Older trucks have had longer to collect them, and popular years draw more because more were sold: no one reports sales by engine, so there's no per-truck rate. Compare the shares below instead.
What owners complain about
Share of this engine's complaints that name each area (one complaint can name several).
What owners write
| Complaints that | Count | Share | Median, other diesel truck engines |
|---|---|---|---|
| Say the engine stalled, shut off or lost power | 163 | 5.0% | 7.8% |
| Mention a "death wobble" | 156 | 4.8% | 0.2% |
| Mention an injector | 81 | 2.5% | 1.2% |
| Mention the turbo | 41 | 1.3% | 1.0% |
| Mention the CP4 or the high-pressure fuel pump | 35 | 1.1% | 0.3% |
| Mention coolant loss or overheating | 18 | 0.6% | 0.8% |
| Mention a fuel leak | 14 | 0.4% | 0.5% |
| Mention an oil leak | 6 | 0.2% | 0.5% |
Counted from the owner's own words in each complaint (all of the truck, not only the engine). A share, not a failure rate.
When problems show up
Half of the owners who gave a mileage reported the problem between 45,000 and 125,000 miles; the middle report was at 80,000 miles (2,247 complaints with a mileage).
Recalls that name this engine 0
No NHTSA recall on these trucks names this engine.
NHTSA recalls on these trucks and years whose text names this engine (its size, or diesel / Cummins / Duramax / Power Stroke). The rest (brakes, air bags, wiring ...) are on each truck year's page.
Trucks with this engine
In owners' words
Abs system doesnt work at all. front brakes when appplied will lock up and rear wheels dont work at all they just roll along. put two set of barke pads on front. almost had four collision.
1999 Ram 2500/3500 (Heavy Duty) owner · NHTSA complaint 9006495
Front brake pads were replaced at 11,000 miles to stop the severe pulling when the brakes were applied---"lockup" started the front wheels lockup and the rears roll free---master cylinder was replaced--porportioning valve was replaced--rear drums were turned & rear shoes were replaced
1999 Ram 2500/3500 (Heavy Duty) owner · NHTSA complaint 9005146
Exterior mirrors vibrate severely when driving over 60-65mph, driver would experience a distorted image of other vehicles in mirror, have contacted manufacturer, and was informed that engineers were working on problem of distortion.*ak
2000 Ram 2500/3500 (Heavy Duty) owner · NHTSA complaint 898706
Against the other diesel truck engine generations
| Engine | Years | Complaints | Name the engine | Name the fuel system | Stalled or lost power | Recalls naming it |
|---|---|---|---|---|---|---|
| 6.0 Power Stroke | 2003–07 | 1,708 | 34% | 16% | 31% | 2 |
| 6.4 Power Stroke | 2008–10 | 572 | 28% | 7% | 11% | 2 |
| Duramax L5P | 2017–26 | 1,229 | 16% | 10% | 14% | 2 |
| 7.3 Power Stroke | 1999–03 | 2,049 | 15% | 5% | 12% | 1 |
| Duramax LML | 2011–16 | 779 | 13% | 20% | 17% | 0 |
| 6.7 Cummins | 2007–26 | 7,667 | 11% | 8% | 6.4% | 9 |
| 6.7 Power Stroke | 2011–26 | 5,640 | 10% | 11% | 7.8% | 6 |
| Duramax LBZ | 2006–07 | 186 | 8% | 5% | 7.0% | 0 |
| Duramax LMM | 2007–10 | 385 | 8% | 6% | 5.2% | 0 |
| Duramax LB7 | 2001–04 | 592 | 7% | 17% | 5.4% | 1 |
| Duramax LLY | 2004–06 | 374 | 7% | 11% | 7.8% | 0 |
| 5.9 Cummins | 1999–07 | 3,245 | 4% | 7% | 5.0% | 0 |
Shares of each engine's own complaints, matched by VIN. They show what owners complain about, not how often trucks break. Every diesel truck engine compared
Quick answers
Is the Cummins 5.9 (Ram) reliable?
No one reports sales by engine, so there's no per-truck score. Of the 3,245 complaints owners filed about trucks with it, 4% name the engine, #12 of 12 diesel truck engine generations we track (1 = the most). 81 (2.5%) mention an injector, against 1.2% for its peers.
What trucks have the Cummins 5.9 (Ram)?
In our data: the Ram 2500/3500 (Heavy Duty), model years 1999–2007, matched by the VIN in each owner complaint.
What are the most common 5.9 Cummins problems?
In owner complaints to the government: steering, airbags, transmission & drivetrain.
How many recalls name the 5.9 Cummins?
0 NHTSA recalls on these trucks name it.
Source: NHTSA owner complaints (FLAT_CMPL + COMPLAINTS_RECEIVED_2025-2026), received through 20261109; engines: NHTSA vPIC VIN decoder; NHTSA recalls API. Engine names and years: Cummins / Ram.