I have a 2006 ford mustang coupe. Yesterday the emission system light turned and has not turned off. Where the mileage usually is it instead says 21 average mph. What does this mean?
it means you have a problem and you need to take it to a mechanic to get the computer scanned. If it were just 1 thing on the car then we could help you but that light could be on for many reasons.
The check engine light comes on for emissions related problems. First thing I would do is make sure the gas cap is on tight. Turn it until it makes a few clicks. Believe it or not it is one of the things monitored by the engine management computer. I won't get into the technicalities but a loose cap can cause the light to come on. Give it a day or two and the light should go out. If the light stays on, then you can download the code(s) by stopping into any one of the big chain auto parts stores; they'll do it for free. All this will do it give you a cryptic code and a very brief system description .which may mean absolutely nothing to you. In which case you need to bring it in to a good local repair shop or the dealership and have a diagnostic run .they will be able to interpret the codes and what needs to be done to service your car. The 21 average mph. is a function of the driver information center. I guess you've not read the owners manual. Most cars made within the last 8 - 10 years or so have a multi-function display where the odometer resides. All sorts of info can be selected to display .average mpg's; instantaneous mpg's, miles to go 'til the tank is empty, how much fuel you've used and .the average speed since you last reset the feature. I suggest you read the owners manual .you might be surprised what you can learn about your car.
