P0204 on GMC
Injector Circuit/Open - Cylinder 4
P0204 on GMC vehicles indicates injector circuit/open - cylinder 4. Au7o has documented this code across 2 GMC models — most commonly on Sierra 2500HD, Sierra 3500HD. This code means the Engine Control Module detected an electrical problem (open circuit or out-of-range resistance) in the fuel injector control circuit for cylinder 4. The ECM controls each injector through its own circuit and monitors it to confirm proper operation. P0204 indicates the computer isn't seeing the expected electrical response from cylinder 4's injector, so that cylinder may not be getting the correct fuel. You'll often notice a misfire, rough running, and a loss of power tied to cylinder 4. Typical repair costs on GMC range from $600 to $6,500, depending on the specific model and root cause.
Common Causes of P0204
- •Damaged or corroded injector connector at cylinder 4
- •Open or shorted wiring in the injector control circuit
- •Failed (electrically open) fuel injector on cylinder 4
- •Loose or backed-out connector pin
- •Poor ground or power feed to the injector
- •Faulty injector driver inside the ECM/PCM
- •Chafed harness causing intermittent open
P0204 on GMC by Model
GMC Sierra 2500HD(1 issue)
- LB7 Duramax Injector Body Cracking and Ball-Seat Erosion Causing Fuel-in-Oil Dilution2001-2004
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.
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.
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View P0204 across all makes →Frequently Asked Questions
What does P0204 mean on GMC?▼
P0204 stands for "Injector Circuit/Open - Cylinder 4." This code means the Engine Control Module detected an electrical problem (open circuit or out-of-range resistance) in the fuel injector control circuit for cylinder 4. The ECM controls each injector through its own circuit and monitors it to confirm proper operation. P0204 indicates the computer isn't seeing the expected electrical response from cylinder 4's injector, so that cylinder may not be getting the correct fuel. You'll often notice a misfire, rough running, and a loss of power tied to cylinder 4. On GMC specifically, this code is documented across 2 models.
What causes P0204 on GMC vehicles?▼
Common causes on GMC: Damaged or corroded injector connector at cylinder 4, Open or shorted wiring in the injector control circuit, Failed (electrically open) fuel injector on cylinder 4, Loose or backed-out connector pin, Poor ground or power feed to the injector. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0204 on a GMC?▼
Repair costs on GMC range from $600 to $6,500, depending on the specific model and root cause.
Which GMC models have P0204 documented?▼
Au7o has documented P0204 on 2 GMC models: Sierra 2500HD, Sierra 3500HD.