P0304 Fault Code on 2010 GMC Sierra: Diagnosis and Solutions
I've been troubleshooting my 2010 GMC Sierra for the past week, and I'm currently dealing with a P0304 diagnostic trouble code. This indicates a misfire in cylinder 4. I'm looking to understand what the normal throttle position percentage (TP%) should be at idle, as this could help identify if the issue is related to engine management or fuel delivery. Any insights on how to properly diagnose and resolve this misfire would be greatly appreciated.
P0304 is a misfire code specifically indicating a problem in cylinder 4. Consider adding one can of Techron or SeaFoam fuel cleaner to the fuel tank to improve combustion efficiency. Check for spark using a noid light on cylinder 4—does the spark appear and flash? Do you have access to an OBD2 scanner with live data? This can help monitor real-time engine parameters. Next step: perform a compression test to rule out mechanical issues in that cylinder. What makes you suspect an RPM-related issue? Can you confirm your idle speed? I believe this is likely related to the TAC (Throttle Actuator Control) system, which operates without a cable—fully electric. A true TAC failure would typically trigger manufacturer-specific codes like P0999 and above. Since only cylinder 4 is affected, it's less likely to be a full TAC issue. Note: Misfires in single cylinders are more commonly caused by faulty spark plugs, ignition coils, or fuel delivery issues.