Hi everybody I am new to this site. Any advice would be appreciated on the stated problem. I have a 3.0L Legacy Lancaster 6 GT 2001 model. Exactly a year ago the engine light came on, I got it diagnosed and it was one of the pre-cat o2 sensors, so I got it replaced. Light off, no problem - until a few days ago.

Same story, light came on and has stayed on ever since, but the car is running sweet. I know that there is a raft of different possibilities as to what it could be, but what I'd like to know is if there is anyone else with the same vehicle that has had the same/similar problem? If so, do you have any advice or tips on solving the problem or what to look for first? Thanks in advance.

Check engine light coming on is entirely normal and common. It's normal for the engine to run perfect with the cel lit.

 

Have the code read. In the us many auto parts chains readncodes for free. You can get a cheap OBD11 scanner on eBay as well and do it yourself for.

My 95 legacy has had a check engine light on for 5 years and i have 301k on it still rinning sweet 2.2 though

Ta for the replies guys. The only snag is: in New Zealand my car must undergo a Warrant of Fitness once a year. If the engine light is on, it will fail and my car will not be roadworthy. It's going in for a code read tomorrow so will take it from there. Will update with the diagnosis and cost to fix.

In the US people routinely clear the code before those inspections.  if you don't pass, you have to fix it and come back, no big deal.  sometimes you can just go to work, clear the code again, drive back tomorrow and pass again.  

 

P0420 code is the most common.  Shops will quote rather large repair bills for catalytic converter. 

 

Make sure you have no exhaust leaks, plugs, wires, air filter, PCV valve are up to date or not problematic (they usually aren't).  Some people try seafoam treatments, etc before going with a catalytic converter replacement. 

Just got the diagnosis, it's the other front O2 sensor, specifically the heating element on the sensor that has failed. The one that was replaced before is fine. I got it reset to see if the CEL stays off but it came back on immediately so it will be a fail on the next warrant of fitness if I don't sort it out. So, I will replace this sensor and hopefully that's the end of it. Cheers for everybody's input.

Running for a long time with a failed o2 sensor can burn out that catalytic.

 

Need the CEL code/s to be sure where to go next.

 

I had a 0420 code caused by a very small exhaust leak.