Friend bought a M55 same time as me. Burns about the same as well...maybe 4 tons between this season as last so far. His stove shuts down now after being fully cleaned with error; hopper over heated, code 4. Installer says it time for the yearly service... I suggested that we post this first to see what might be the problem, and maybe we could fix it. Yearly service is $175.00....this is worth a shot.