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My Evo 9 got CEL P0420 Catalyst System Efficiency Below Threshold (Bank 1) with the new catalyst converter . ( the old cat gone bad that's why i had that changed ) , I searched online and the saw that is because of the aftermarket cat need a defouler . After installed the defouler, CEL P0420 is gone but now i got CEL P0133 Oxygen Sensor Circuit Slow Response (Bank 1, Sensor 1)
So, i am not sure if I should change the front O2 sensor ? or I need a OEM cat ? anyone had similar problem ?
Any suggestion would be greatly appreciated !
Change the front o2. They go bad often. You can get it cheap on rockauto.com
Is Denso reliable and function just like Mitsubishi OEM parts ? now i just realized my Evo has more CEL,
so here is my story and i need some help and opinion how to get all CEL fixed
Here is my story, my Evo 9 has been with CEL on before, i ran my small actron cp9550 scanner and knowing i have at least 2 CEL. P0171 , P0420 and P0133
Last week i cant start the engine, after 4-5 times attempt I can get it to run but with rough idle rev and stall when i give gas. So I have it towed to the autoshop and asked them to fix the problem and diagnose the CEL so i can pass the NYS inspection
Problem is when i pick up the car, they said they only see 1 CEL P0171 which i know that is not the case, they failed diagnose all CEL , it should be easy enough run a scanner to diagnose and tell me all CEL at the beginning.
My evo is now with CEL P0171 , P0133 and P0420, apparently my small actron cp9550 scanner didnt show P0420 is still here.
They said they only fixed P0171 and charged me huge mark up for Denso idle control valve for $434 and air mass meter for $613, price were close to Mitsubishi OEM parts, which i original thought they use Mitsubishi OEM.
My Evo now have weak start when start the engine and idle go rough a little after it warmed up. also with 3 CEL P0171 , P0420 and P0133 ( my small scanner showed P0171 and P0133, then after they rebooted and I drove 30-40 miles it now show P0171 and P0420, I am assuming it just cant show more than 2 codes at a time i guess ) I just dropped off the car to the autoshop to have them to fix the weak start and rough idle . also P0171 suppose to be gone as they said they only saw it from the beginning .
I may want to dispute and charge back if they fail to fix the P0171 and weak start / rough idle plus they failed to diagnose all the CEL from beginning.
I hope to get some feeback from you guys what is the best move i should do to get all CEL fixed ? go to Mitsubishi service center maybe a better move ? at least they use their OEM parts
or should i bother to research online and get cheaper part online myself and bring it to better reputation shop to install them for me ?
Last edited by emuleiii; May 23, 2018 at 07:31 AM.
Thumps up for the Denso o2 sensor... FYI, after taking out the factory o2 sensor and inspecting it, it was a DENSO sensor! That's OEM in my book but the OEM one online is upwards of $340 or so.
For the downstream o2 sensor, I used a spark plug defouler (that was drilled out to fit the o2 sensor)... however, this only manipulates the reading to not kick off the CEL. There are other defoulers you can buy but again, I went with the 5 dollar DIY.
Thumps up for the Denso o2 sensor... FYI, after taking out the factory o2 sensor and inspecting it, it was a DENSO sensor! That's OEM in my book but the OEM one online is upwards of $340 or so.
For the downstream o2 sensor, I used a spark plug defouler (that was drilled out to fit the o2 sensor)... however, this only manipulates the reading to not kick off the CEL. There are other defoulers you can buy but again, I went with the 5 dollar DIY.
Confirmed. For my P0134, new upstream Denso o2 sensor (got mine from Autozone after driving around town to 2 other parts stores)... and CEL hasn't popped up yet. I cleared it myself with the OBD II scan tool.
Confirmed. For my P0134, new upstream Denso o2 sensor (got mine from Autozone after driving around town to 2 other parts stores)... and CEL hasn't popped up yet. I cleared it myself with the OBD II scan tool.
Which brand is your OBD II scanner ? I have Actron pocketscan plus CP9550 , which seems like it can only pick up 2 codes at a time. I had P0171 , P0133 before and then after resetting battery and drove for 30-40, now i have P0171 and P0420 . but i know P0133 O2 sensor problem is not fixed, so i suspect my scanner cant pick up all the code at once
I have the bluetooth OBD scan adapter and run a free app called Torque... I couldn't tell you if it's better or not but it works for me. Have you tried to clear the fault codes and see if any others pop up?(see that you are concerned that you have other possible codes being tripped) I hope you figure out your whip soon Brother! Here is a pic of my setup...
Samsung Tab A 11 8nch with Torque Lite app running
P0133 is front O2 sensor slow response. P0171 means the engine is running lean. P0420 is a non working catalytic converter. Each one of these codes can be due to bad wiring, a failed or failing sensor or an actual problem. P0133 MAY be related to the P0171. A failing rear O2 sensor MAY set a P0420.
P0133 is front O2 sensor slow response. P0171 means the engine is running lean. P0420 is a non working catalytic converter. Each one of these codes can be due to bad wiring, a failed or failing sensor or an actual problem. P0133 MAY be related to the P0171. A failing rear O2 sensor MAY set a P0420.
You are pretty good with these CEL, I first got P0420 early last year and that should do with catalytic converter, which i changed a aftermarket cat - ultimate-racing Evo VIII/IX High-Flow Cat (Ceramic), but the CEL P0420 still come on. then adding a defouler on O2 sensor on the cat to try to get rid of it , but defouler failed to take off the CEL . I emailed ultimate-racing.com and they said a tune or flash can take care of it but i dont know how to do those ?
My Actron pocket scanner also show I/M reading - Oxygen sensor is not ready, does that mean that is front O2 senor need to be replaced , relate to code P0133 O2 sensor slow?
I may have a dispute with the autoshop, they need to fix P0171 for sure as I specific mentioned that CEL need to be fixed so i can pass NYS inspection and they claimed they only saw P0171 engine lean at the beginning and charged me for parts- Denso idle control valve $ 400ish and Mass air filter $600ish, not Mitsubishi OEM and still failed to clear the CEL. I dont understand how they can just failed to see all codes from the beginning? playing trick to rip me off ?
I hope it is true that P0171 go away with P0133, because I only have P0420 last year when i scanned it myself
Last edited by emuleiii; May 23, 2018 at 10:54 AM.
If I were a shop mechanic and presented with this car with these codes, the first thing I’d do is connect a scanner and watch the performance of the O2 sensors. There’s a specific pattern I’d expect to see, front and rear. I’d also be watching the fuel trims, seeing how far they vary from zero. Hopefully, that would provide the clues needed to point to what to start checking.
I don’t know anything about the after market catalytic converter you installed, some work, some don’t. A good mechanic in New York state is going to want to install an OEM converter and reinstall the rear O2 sensor. They fine the inspection shops big time in your state if they catch them cheating. This could be an expensive repair.
May 22, 2018, 06:09 AM
