The P0203 code on your 2023 Chevrolet Silverado indicates a detected malfunction in the cylinder 3 fuel injector circuit. The ECM monitors each injector circuit and sets specific codes when problems are found, allowing targeted diagnosis.
Finding Cylinder 3 on Your Silverado
GM's cylinder numbering places odd cylinders (1, 3, 5, 7) on the driver's side bank and even cylinders (2, 4, 6, 8) on the passenger side. Cylinder 3 is the second cylinder from the front on the driver's side. This applies to the 5.3L, 6.2L, and 3.0L Duramax engines.
Circuit Malfunction Causes
The ECM triggers P0203 when it detects incorrect current flow in the cylinder 3 injector circuit. This could indicate an open injector coil, shorted wiring, damaged connector terminals, or a failed injector driver in the ECM (rare). On direct injection engines, injector tip failure can also cause circuit anomalies.
Systematic Testing
Start with a simple injector resistance test—disconnect the injector and measure coil resistance with an ohmmeter. Compare to specifications for your specific engine. Perform a voltage drop test on the power and ground sides of the circuit. Use GM's GDS2 software to perform an injector flow test if available. Swap the injector with an adjacent cylinder to confirm whether the fault follows the component.
Completing the Repair
Injector replacement on modern Silverados requires removing the fuel rail assembly. Depressurize the fuel system before disconnecting any fuel lines. Use new O-rings and seals during installation. The 3.0L Duramax diesel has different injector procedures—consult diesel-specific repair information.