2004 Chevrolet Silverado 4.8L with P0300 and P0135 Codes After O2 Sensor and Catalytic Converter Replacement
My 2004 Chevrolet Silverado with a 4.8L engine has reached 120,000 miles. Recently, I had both the catalytic converter and oxygen (O2) sensors replaced. Approximately 100 miles later, the service engine light activated, and the vehicle is now displaying P0300 (random misfire) and P0135 (O2 sensor circuit malfunction). A noticeable ticking noise is present, which intensifies as RPM increases. While I'm cautious about making assumptions, I'm wondering if spark plugs should be inspected—could a failing ignition system be contributing to the misfires? The O2 sensor code may indicate improper fuel combustion, especially given the age and mileage of the vehicle.
It's important to verify whether the replacement parts were sourced from the dealer or an aftermarket brand. Some aftermarket oxygen sensors can trigger a P0135 code due to compatibility issues or sensor performance problems. Regarding the random misfire (P0300), when was the last time a full tune-up—such as spark plugs and ignition wires—was performed? This could be a key factor in diagnosing the issue.