⚠️ GMC manufacturer position
Truck tank access is documented in GMSI by cab, bed, and tank package. Contamination is customer misuse.
Vehicle information
| Make | GMC |
|---|---|
| Model | Sierra |
| Market status | Sold new in the US 1999–present |
| Body styles | Full-size pickup truck |
| Generations | GMT K2XX, T1XX light-duty and HD variants |
| Engine options | Gasoline: 5.3L V8, 6.2L V8, 2.7L turbo (availability varies) Diesel: 3.0L Duramax (1500) and 6.6L Duramax on HD models where equipped Electric: Sierra EV (no fuel tank) |
| Fuel tank capacity | 25.9 gal typical (varies by tank option) |
| Fuel system | Gasoline injection or Duramax common-rail diesel with DEF on diesel |
| Access method | Tank drop or OEM truck access—consult GMSI |
| Anti-siphon | Yes |
| Service portal | GM Service Information (GMSI) / ACDelco TDS |
Misfuel risk High
Sierra diesel pickups are a core US gasoline-in-diesel misfuel exposure—especially fleet and towing customers.
If the engine was not started
Keep keys away from start button if gasoline entered a diesel tank.
If the engine was started
Diesel HP fuel system overhaul may be required; document all replaced components.
Access procedure
- Depressurize the fuel system per GM service information; disconnect battery negative.
- Access fuel module via under-seat/trunk panel or perform tank lowering if required for the platform.
- Disconnect electrical connector and fuel line fittings; use line plugs as specified.
- Remove lock ring and lift module; extract wrong fuel with approved recovery equipment.
- Inspect tank and lines; replace filters if contamination reached the engine supply circuit.
- Reinstall module with new seal; verify connections and perform leak check.
- Prime system and clear DTCs per GMSI before returning vehicle to service.
Notes
- Denali and AT4 trims use the same fuel system service procedures as other Sierras.
Related models
- Chevrolet Silverado
Frequently asked questions
Does the Sierra HD use the same diesel as the 1500?
HD models may use the 6.6L Duramax while many 1500s use the 3.0L—fuel procedures differ by engine; confirm in GMSI.
Can mobile extraction siphon a Sierra tank?
USIFDA certified work follows GM OEM access methods, not undocumented filler-neck siphoning.
Need professional misfuel recovery?
Find a certified operator or read consumer guidance for your next steps.
Find an operator Consumer guidance