my mother also has a 2003 lancer oz and she has been having issues with the cel coming on every time we have it read it comes up with code 456 (small evap leak).
she was told it was prob her gas cap... she bought a new one and still gets the CEL.
she brought it to a garage and they used a machine and put smoke through her evap system and they found no leaks. we and the machanic are stumped now

I figured I would ask here and see if anyone happens to have any ideas or if someone has dealt with this before.

 

did u guy try reseting ecu by disconnecting the battery after u fixed that gas cap,try to reset the ecu and see if it comes back

 

we haven't tried this but the mechanic cleared the codes while the car was in the shop.... wouldn't this do the same thing?

 

Check the evap purge valve for leakdown. This is the most common cause of this code. If nothing, try replacing the gas cap (with OEM only!).

 

the mechanic did check the evap purge valve and it was fine... I think she bought the gas cap from auto zone so its not oem... I will take the gas cap off of my lancer and put it on her car and see if it fixes it

 

just figured I would update... I reset the ECU on friday and the CEL has yet to come back on. hopefully this fixed the problem. thanks for the help guys

 

I spoke to soon..... the light came back on today

 

any other ideas?

 

still looking for help with this