If your odometer is that dim, you blew a fuse.
Which one? Well... my memory ain't that good.

 

I'm not sure what year OZ you're driving thedeatons, but I got my 2003 5-spd back in early may. Bought it used from a guy in new york (i'm from NJ) and after driving it back from NY and halfway around NJ (lol) i got about 3 miles from home and the SES came on :-p you can imagine how amused I was to see that no less than about 8 hours after I bought the car.

I had bought an OBD-II program for my laptop (not bad software) and checked out the codes for myself to find P0421 - Low Catalyst Effeciency Threshold, Bank 1 Sensor 1. I looked up TSBs on AllData and found that there is a recall on the 2003 OZ Lancer (i don't remember if it was to all Lancers but i would be willing to bet it was). The recall was on the Lancer ECU, there were certain parameters that would keep killing the catalytic converters.

I managed to get my car to the dealership just at 79,500 miles. Just in time for the 8 year, 80,000k mile law. So everything was free-the new cat and the ECU reflash. Not sure if that's what is going on with yours, but I figured I would pass on my experience.

 

I had mine done at 109k miles. I still have this problem after they reflashed my ecu and replaced some relay thing. I gave up and just plan to put on headers and high flow cat. The hell with fixing it.

 

You would care when car starts acting funny and getting poor gas mileage
You can add a spark plug anti fouler to fix P0421. I did this to my car and it's been nearly 2 years now without that fault coming back.
Reason it came on for me was because I added an obx header deleting the first cat.

https://www.evolutionm.net/forums/ev...cel-light.html

 

A CEL most certainly WILL affect fuel economy. When the light is on, the computer reverts to L.O.S. mode (Limited operation strategy) which is essentially a "limp mode" designed to make the car run safely but not efficiently. This limp mode has a much richer fuel map, which accounts for the decrease in mileage.