P0203 on GMC
Injector Circuit/Open - Cylinder 3
P0203 on GMC vehicles indicates injector circuit/open - cylinder 3. Au7o has documented this code across 1 GMC model — most commonly on 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 3. The ECM pulses each injector electrically and watches the circuit to verify it is operating. P0203 means the expected feedback for cylinder 3's injector is missing or abnormal, so that cylinder may not be fueling properly. The typical result is a misfire, rough idle, and reduced performance traceable to cylinder 3. Typical repair costs on GMC range from $600 to $5,000, depending on the specific model and root cause.
Common Causes of P0203
- •Damaged or corroded injector connector at cylinder 3
- •Open or shorted wiring in the injector control circuit
- •Failed (electrically open) fuel injector on cylinder 3
- •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
P0203 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.
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View P0203 across all makes →Frequently Asked Questions
What does P0203 mean on GMC?▼
P0203 stands for "Injector Circuit/Open - Cylinder 3." 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 3. The ECM pulses each injector electrically and watches the circuit to verify it is operating. P0203 means the expected feedback for cylinder 3's injector is missing or abnormal, so that cylinder may not be fueling properly. The typical result is a misfire, rough idle, and reduced performance traceable to cylinder 3. On GMC specifically, this code is documented across 1 model.
What causes P0203 on GMC vehicles?▼
Common causes on GMC: Damaged or corroded injector connector at cylinder 3, Open or shorted wiring in the injector control circuit, Failed (electrically open) fuel injector on cylinder 3, 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 P0203 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 P0203 documented?▼
Au7o has documented P0203 on 1 GMC model: Sierra 3500HD.