engine codes p0136, p2270, and p0420

At first the p0136 code showed up on my 01 V6 Tacoma, so I replaced the rear O2 sensor and the engine light went out. Then about a month later the engine light came back on for a week and then went off and this happened a couple times until it stayed on. Now the codes that pop up are the p0136, p2270, and p0420 all in combo. If anyone could give me a better idea of what's actually wrong I would be greatfull.

 

P2270- O2 sensor stuck lean. This is usually caused by an exhaust leak, misfire or badly out of calibration fuel injection system.The code usually shows up alone as the computer ignores this problem if it sees a misfire and brings up that code instead.

Code P0420 means "Catalyst System Efficency Below Threshold (Bank 1)"P0420 is actually Catalyst System Efficiency Below ThresholdCatalyst System Efficiency Below Threshold.This means that the secondary O2 sensor detects that the catalytic converter isn't working as efficiently as it should.This engine code can be triggered by any one of the following: 1.) The catalyst in the catalytic converter is cracked, clogged, or otherwise damaged. 2.) The secondary O2 sensor is malfunctioning. 3.) There is an exhaust leak. 4.) The computer unit is faulty.Trouble code P0420 means: Catalyst Efficiency Below Normal (Bank 1).

Code p0136- O2 sensor malfunction, Bank 1 sensor 2.

Here's my guess, either out of timing or spark issues and misfiring may have caused the lean condition OR a small exhaust leak caused a lean condition in the catalyst. This damaged the catalyst and you are now getting post catalyst trim readings from the o2 sensor. Replacing the sensor would be the last thing to do. It's failing because of something else. My .02 is it may be the catalyst that's causing the issues, but then you also need to find out what damaged the catalyst in the first place.

 

Did you get anywhere with this?

 

I did end up finding a hole in my muffler, which is most likely the cause of my problems.