Hummer H2 P003 code with multiple cylinder misfire issue on Hummer H2

Some Hummer H2 owners report experiencing issues related to the P0300 code, which signifies a random or multiple misfire in the engine that can threaten vehicle drivability. This code is often accompanied by specific cylinder misfire codes, such as P030X, indicating the exact cylinder experiencing the misfire. If the last digit of the diagnostic code is not zero, it points to a specific cylinder misfire, like P0302 for cylinder two. Owners have noted that replacing various components, including catalytic converters and spark plugs, did not resolve the ongoing P0300 codes, highlighting the importance of thorough diagnostics to address root causes. Additionally, some have found that resolving unrelated issues, such as replacing the coolant thermostat, can inadvertently lead to misfires and the P0300 code. Specific problems, particularly with cylinders 1 and 5 in the 2006 3.5L model, can occur due to worn seals on coil packs, allowing water or oil intrusion that leads to misfires. It is essential for owners to address these underlying issues to effectively resolve the P0300 code and ensure the engine functions properly.