P0263 on GMC
Cylinder 1 Contribution/Balance
P0263 on GMC vehicles indicates cylinder 1 contribution/balance. Au7o has documented this code across 1 GMC model — most commonly on Sierra 3500HD. This code means the engine computer has detected a contribution or balance problem on cylinder 1, indicating that this cylinder is producing more or less power than the others. The computer monitors tiny speed changes from each cylinder's firing event and flags one that is contributing unevenly. It points to a fueling, compression, or mechanical imbalance specific to cylinder 1 (and, on some diesels, a related fuel injector circuit). You may notice rough idle, a misfire feel, or reduced power. Typical repair costs on GMC range from $600 to $5,000, depending on the specific model and root cause.
Common Causes of P0263
- •Faulty fuel injector on cylinder 1
- •Clogged or leaking cylinder 1 injector
- •Low compression in cylinder 1 (valves, rings, head gasket)
- •Worn or fouled spark plug / coil on cylinder 1 (gas engines)
- •Injector wiring or connector fault on cylinder 1
- •Vacuum or intake leak affecting that cylinder
- •Carbon buildup or sticking valve on cylinder 1
P0263 on GMC by Model
GMC Sierra 3500HD(1 issue)
- Diesel Injector Failure Causing White Smoke and Rough Running2015-2024
The Bosch piezoelectric fuel injectors on the Duramax L5P and LML engines can fail due to contaminated fuel, high-mileage wear, or internal electrical faults. A failed injector causes white smoke on startup, rough idle, misfires on the affected cylinder, and fuel dilution of the engine oil. The high fuel rail pressures (up to 36,000 PSI on the L5P) stress the injectors over time. Contaminated fuel from bulk diesel stations accelerates injector wear.
Looking for P0263 on a different make?
View P0263 across all makes →Frequently Asked Questions
What does P0263 mean on GMC?▼
P0263 stands for "Cylinder 1 Contribution/Balance." This code means the engine computer has detected a contribution or balance problem on cylinder 1, indicating that this cylinder is producing more or less power than the others. The computer monitors tiny speed changes from each cylinder's firing event and flags one that is contributing unevenly. It points to a fueling, compression, or mechanical imbalance specific to cylinder 1 (and, on some diesels, a related fuel injector circuit). You may notice rough idle, a misfire feel, or reduced power. On GMC specifically, this code is documented across 1 model.
What causes P0263 on GMC vehicles?▼
Common causes on GMC: Faulty fuel injector on cylinder 1, Clogged or leaking cylinder 1 injector, Low compression in cylinder 1 (valves, rings, head gasket), Worn or fouled spark plug / coil on cylinder 1 (gas engines), Injector wiring or connector fault on cylinder 1. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0263 on a GMC?▼
Repair costs on GMC range from $600 to $5,000, depending on the specific model and root cause.
Which GMC models have P0263 documented?▼
Au7o has documented P0263 on 1 GMC model: Sierra 3500HD.