P1093 on GMC: How to Diagnose & Fix
Fuel Rail Pressure Low During Power Enrichment / Fuel Rail Pressure Too Low (manufacturer-specific)
1 GMC model · 1 documented issue · 1 critical · $3,500-$6,500 repair
P1093 on GMC by model: symptoms, diagnosis and fix
The 2001-2004 6.6L Duramax RPO LB7 uses injectors buried under the valve covers that are notorious for failing well before 150,000 miles. GM's own analysis attributed the failures to fuel injector body cracks, ball seat erosion, and high-pressure seal extrusion. A leaking injector dumps unburned diesel into the cylinder and past the rings into the crankcase, raising the oil level and diluting it. Owner reporting on duramaxforum.com and silveradosierra.com consistently puts first failures in the 100k-150k range, and because the injectors sit under the valve covers the labor to reach them is far higher than on the later LLY/LBZ engines, where injectors are accessible from the top. This is an LB7-only failure mode - the LLY and later injectors were redesigned and do not share it.
Common Symptoms
- White or blue smoke at idle once warmed up
- Strong raw fuel smell from the exhaust
- Engine oil level rising between changes and smelling of diesel
- Rough idle and misfire, especially cold
- Hard starting
- Knocking/rattle under load
How to Fix
Replace all eight injectors as a set (replacing one at a time invites repeat teardown labor), along with the injector return lines and valve cover gaskets. GM issued a Special Policy extending injector coverage to 7 years/200,000 miles for qualifying trucks after a dealer balance-rate test - that program has long expired, so repairs are now owner-paid. Reman Bosch or new injectors plus the required ECM injector-code programming is the correct repair; change the oil immediately afterward because of the fuel dilution.
Sources for this issue (3)
P1093 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P1093 mean on a GMC?
P1093 stands for "Fuel Rail Pressure Low During Power Enrichment / Fuel Rail Pressure Too Low (manufacturer-specific)." P1093 is a manufacturer-specific powertrain code indicating insufficient fuel rail pressure. On GM gasoline applications it is typically 'Fuel Rail Pressure Low During Power Enrichment,' meaning the rail could not maintain the pressure the computer commanded during hard acceleration. On many diesel and other applications it is reported as 'Fuel Rail Pressure Too Low' or a fuel rail pressure sensor circuit fault. Low rail pressure can cause hesitation, power loss, and potential lean operation, so it should be addressed promptly. On GMC it is documented across 1 model: Sierra 2500HD.
What are the most common causes of P1093?
The most common causes of P1093 are: Weak or failing fuel pump (lift or high-pressure pump), Clogged fuel filter or restricted fuel supply line, Faulty fuel pressure regulator, Faulty fuel rail pressure sensor or wiring, Leaking or returning fuel injectors, Low fuel volume / restricted fuel delivery under load, Air or leaks in the fuel system. The specific cause varies by vehicle.
How much does it cost to fix P1093 on a GMC?
Published repair estimates on GMC range from $3,500 to $6,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P1093 on a different make?
View P1093 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.