if you have access to a scan tool you need to read the sensors and see whats going on.oxygen sensors, and air and coolant temp sensors, maybe a thermostat if engine is running cold, cold engine requires more full. NO code will set if it is within operating parameters. The v-6 is not a fuel efficient engine. you are probably only off by 1 or 2 mpg's. I've had my 2000 dakota since new,best I ever saw was 14. Michigan is colder than you are,and I use remote start, I am seeing about 9mpg's right now. driving is about 50 /50 between city and freeway.