Have a 1993 Suburu Legacy with 192k, was overheating so did everything (water pump, temperature sensor, thermostat, radiator, etc.) To fix including new headgaskets on each side and new spark plugs and wires. Then got back from mechanic and temperature gauge was not moving at all and then engine light started blinking. I triple checked that all were correct parts and checked mechanics work. Mechanics are good but had old decoder. What do you think it could be? Engine is running good and smooth. Car is driving smoooth so its frustrating. Please give me some possibilities as I am baffled?