# '03 Mits **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** mitsubishi, lancer\ **Created:** [December 27, 2011, 2:51am UTC](https://community.cartalk.com/t/03-mits/70135 "2011-12-27T02:51:23Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![janeyschaz](https://avatars.discourse-cdn.com/v4/letter/j/c89c15/32.png) [@janeyschaz](https://community.cartalk.com/u/janeyschaz)\ **Post date:** [December 27, 2011, 2:51am UTC](https://community.cartalk.com/t/03-mits/70135/1 "2011-12-27T02:51:23Z")
2003 Mits. Lancer, ES. Service engine light been on 6 months. Had it scoped twice, both reported “warm up catalyst efficiency below threshold bank 1.” One shop wants 800 bucks for repair. Still getting 30-plus mpg. Are there any other options? janeyschaz ---
**Author:** ![Honda-Blackbird](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/honda-blackbird/32/3159_2.png) [@Honda-Blackbird](https://community.cartalk.com/u/Honda-Blackbird)\ **Post date:** [December 27, 2011, 3:52am UTC](https://community.cartalk.com/t/03-mits/70135/2 "2011-12-27T03:52:39Z")
Clear your code…by disconnecting the pos terminal of the batt…give it a few minutes and hook it back up and monitor. If it comes back you may have an issue with an o2 or a mixture sensor. In the cold most people just take off and force every part of the engine to warm up as well… I see most if not ALL of the O2 sensor issues in cold weather…either the heater circuit this or heater circuit that…etc… I ALWAYS clear the codes to see if they return hard…if they continue to return on the same code I act on it… Your code points to the efficiency of the cat…the cat is expensive and rarely go bad…this issue is most likely a discrepancy between the pre and post cat O2… This can occur for several reasons… Clear the codes and monitor…see what you get before you act. Blackbird ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [December 27, 2011, 5:00pm UTC](https://community.cartalk.com/t/03-mits/70135/3 "2011-12-27T17:00:20Z")
Have the codes read again. This time write down the exact code - e.g. “P1234” and post that. Have the codes cleared after reading them to see if the light comes back. For the moment I’ll assume the code is P0421 & the shop is quoting you a price for a new catalytic converter. If that’s the case then one thing you want to do is call a few other shops to get estimates - just tell them the diagnosis & that you’re just looking for a ballpark idea. But the other thing you want to do is make sure that you’re getting it looked at by a reputable & trustworthy shop known for its expertise in diagnosis as there are a couple of things to be careful about. One is that, as HB noted, the code is actually set because of reports from O2 sensors. A lot of shops will see such a code & just assume a bad converter, but the O2 sensors should be checked first. A second thing is that if it ends up being a bad catalytic converter then someone should find out what killed it. There’s probably a reason & if the underlying cause isn’t addressed you’ll just kill the new one too. Do you do a lot of short trip driving? ---
**Author:** ![Honda-Blackbird](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/honda-blackbird/32/3159_2.png) [@Honda-Blackbird](https://community.cartalk.com/u/Honda-Blackbird)\ **Post date:** [December 27, 2011, 7:04pm UTC](https://community.cartalk.com/t/03-mits/70135/4 "2011-12-27T19:04:38Z")
Very true… Cigroller is right… get a good diagnostic shop to look at it…and if you don’t do this yourself…go into the shop pre-armed with the knowledge that cats don’t go bad that often…the code you have can and usually is a discrepancy between two O2 sensors…SAY THAT TO THEM…that way the shop will be less likely to throw you a red herring… ---
**Author:** ![janeyschaz](https://avatars.discourse-cdn.com/v4/letter/j/c89c15/32.png) [@janeyschaz](https://community.cartalk.com/u/janeyschaz)\ **Post date:** [January 3, 2012, 2:00am UTC](https://community.cartalk.com/t/03-mits/70135/5 "2012-01-03T02:00:52Z")
RE Mits. Lancer, thanks ya’ll, very much. Each time I had the code read, they turned the light off. It came back each time within days. Will go forward with 02 sensors, thanks again JS