spyderdog

hi!

forgive me if this has been posted before (im new)

my 02 lancer ES has just failed emissions and P0137 EGO Sensor Circuit Low Voltage (Bank 1 Sensor 2), and P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1) were cited as the issues.

im assuming that the P0421 means i need to replace a cat, and P0137 means o2 sensor. my question is which one, and is there any other cheaper alternatives by adding additional aftermarket?

i live in the phoenix area (no cali or ny issues) and the car has 137k with no open recalls. the car has a no name short ram intake and a no name aftermarket muffler (attached to the factory pipe), both very poorly installed by methed out juggalos (the previous owners, previous owners), but they both seem to be functioning ok

any information would be greatly appreciated!

thanks in advance!

BlueGoat

The P0421 is usually caused by a bad signal from the rear oxygen sensor. Which differs from the front sensor. The catalytic converter purifies exhaust gas so when its bad or really old the signal from the front sensor becomes similar to the rear heated oxygen sensor causing the code. The other code is most likely the front sensor if I remember correctly. Also it has been known to throw the 137 code due to a bad MAF. Try cleaning yours.

I would buy a Cat off-line and have it welded in. I did that on my 06, much cheaper then buying the cat from a dealer. O2 sensors are not to much I would replace both if you can. But start with the back one after you get the new cat.

02modlanceroz

iTrader: (2)

The P0421 is a recall on the Mitsubishi for bad software that causes the pre-cat to overheat and damage the cat. This is the catalytic converter that is built in the exhaust manifold. A new header and updated software will fix the problem. However, if it was me, I would replace the header with an aftermarket header that doesn't have a cat and get a CEL eliminator to use for the downstream o2 sensor.

spyderdog

no open recalls currently on this car. had it at the dealer to check the other day

spyderdog

****!

i wasnt looking at the paperwork when i was typing this up, im looking at a P0134, not a P0137

my apologies!

02modlanceroz

iTrader: (2)

p0134 means that the o2 sensor in bank 1 sensor 1 has no activity. Either a problem with the wiring or a faulty o2 sensor. this is the one that goes in the exhaust manifold.

spyderdog

found some monkey business with the way the intake was installed by the previous owner. P0134 is now gone, but the P0421 remains.......

02modlanceroz

iTrader: (2)

http://mitsubishiforum.com/forum/mit...-recall-32516/

You probably aren't going to find a dealer that is going to do the recall work on it and you're probably over the mileage for the recall. Like I said, if it were me, I would replace the manifold with an aftermarket header from RRM or maybe something on Ebay and then buy a CEL eliminator to use to trick the downstream o2 sensor. Me personally, when I bought the RRM header their CEL eliminator didn't work. I bought 2 anti foulers off of Ebay for spark plugs. Drilled one out with a 1/2" drill, screwed my o2 into that one and then screwed the o2 sensor and antifouler into the other antifouler and placed all of that back into the o2 bung.

spyderdog

as stated, already been to the dealer. the flash was done and theres no additional open recalls