The Lemon Index
The 6.6 L V8 turbo diesel in the Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD, model years 2017–2026. Owners filed 1,229 complaints about trucks with it (matched by VIN); 16% name the engine, #3 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):
- The DPF / DEF / NOx sensors. 72 of 1,229 owner complaints (5.9%) mention the DPF, DEF or regen system, against a median of 0.1% for the other diesel truck generations we track.
I purchased my vehicle in 2019. Since then, I have had several issues. I've had to replace the coolant reservoir, DEF heater/pump and twice changed the number 8 injector plug. The warning light came on just after the warranty went out. The code reader read the ambient sensor and no sensor.
2019 owner · NHTSA complaint 11661793
Also often talked about, but not standing out in complaints to NHTSA: fuel leaks (3 of 1,229, 0.2%, peers 0.5%). 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 41/100 across 9 model years, from 166 videos about this engine and its cars.
Most-watched videos
- 2024 Duramax L5P Engine First Look And Comparison | Banks Exclusive 962,045 views
- 2020 DURAMAX L5P Engine Revealed! 655,108 views
- WARNING! Service Emissions System! Speed Locked Out! DPF Forced Regeneration 6.6 DURAMAX L5P 458,852 views
- FULLY DELETED L5P!!!!....WOW 440,607 views
- Our FAVORITE Upgrades For An L5P Duramax! 433,359 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 | 175 | 14% | 7.8% |
| Mention the DPF, DEF or regen system | 72 | 5.9% | 0.1% |
| Mention coolant loss or overheating | 52 | 4.2% | 0.8% |
| Mention an injector | 32 | 2.6% | 1.2% |
| Mention the oil cooler | 9 | 0.7% | under 0.1% |
| Mention the CP4 or the high-pressure fuel pump | 8 | 0.7% | 0.3% |
| Mention the turbo | 7 | 0.6% | 1.3% |
| Mention an oil leak | 6 | 0.5% | 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 8,501 and 62,000 miles; the middle report was at 26,000 miles (329 complaints with a mileage).
Recalls that name this engine 2
21V496000 Jul 2021 Equipment
General Motors, LLC (GM) is recalling certain 2017-2019 Chevrolet Silverado 2500, 3500 and 2017-2019 GMC Sierra 2500 and 3500 vehicles equipped with a Duramax diesel 6.6 liter engine and an optional engine-block heater cord. An electrical short-circuit may occur in the engine-block heater cable or in the terminals that connect the heater cable to the block heater.
Fix. Dealers will replace engine block heaters and heater cords. Vehicles that have this feature disabled as a remedy to the safety condition will be contacted and offered replacement block heaters and heater cords under a separate customer satisfaction program, free of charge. GM will provide free replacement block heaters and cords under a separate customer satisfaction campaign. For vehicles previ
19V328000 Apr 2019 Engine
General Motors LLC (GM) is recalling certain 2019 Chevrolet Silverado 4500, 5500 and 6500 vehicles and 2017-2019 Chevrolet Silverado 2500 and 3500 vehicles and GMC Sierra 2500 and 3500 vehicles equipped with Duramax 6.6 liter diesel engines and an optional engine-block heater. The engine block heater cord or the terminals that connect the heater cord to the block heater may short circuit and fail.
Fix. GM will contact owners, dealers will replace the engine block heater, free of charge. Additionally, in Chevrolet Silverado 2500 and 3500 vehicles, dealers will install a new rerouted heater cord. The recall began December 11, 2019. Owners may contact GM customer service at 1-586-596-1733. GM's number for this recall is N182206310.
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
My 2026 Chevrolet Silverado 2500 HD has suffered three original Goodyear tire sidewall failures within 13,290 miles. One failure damaged a rear hydraulic brake line while driving. Serious safety hazard.
2026 Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD owner · NHTSA complaint 11773653
My rear spoiler roof area leaks. This is something GM knows about and has sent out memos to dealers. To fix this it’s around $1000. I think GM should fix a problem they have been well aware of for sometime.
2020 Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD owner · NHTSA complaint 11769733
Service Trailer Brake System error. There's a known issue for a faulty wire harness and BCM. Error makes it hard to drive and see the speed, keeps popping up.
2021 Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD owner · NHTSA complaint 11769417
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 Duramax L5P reliable?
No one reports sales by engine, so there's no per-truck score. Of the 1,229 complaints owners filed about trucks with it, 16% name the engine, #3 of 12 diesel truck engine generations we track (1 = the most). 72 (5.9%) mention the DPF, DEF or regen system, against 0.1% for its peers.
What trucks have the Duramax L5P?
In our data: the Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD, model years 2017–2026, matched by the VIN in each owner complaint.
What are the most common Duramax L5P problems?
In owner complaints to the government: transmission & drivetrain, electrical, engine.
How many recalls name the Duramax L5P?
2 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: GM (RPO codes).