Active Fuel Management (AFM) is a system used by General Motors to improve fuel economy. The system allows the engine to run on four cylinders when less power is needed, such as during highway cruising. This reduces fuel consumption and emissions.
Unfortunately, there is no way to bypass AFM. The only way to disable it is to install a special tune that disables the feature. However, this will likely void your warranty and may cause other issues. We do not recommend doing this unless you are an experienced mechanic or tuner.