code p0136

Check engine light came on with code p0136. Replaced downstream 02 sensor with a new denso. Next day CEL came back on with same code. Replaced sensor again with another new denso. Next day CEL is back on with same code. Engine is running fine but smells like it's running rich. Any help would be greatly appreciated! My truck is a 2004 tacoma sr5 extended cab 4wd.

 

It could be a vacuum leak in the intake, leaky exhaust near the sensor, bad wiring to/from the ECU.

 

Are you running stock exhaust or aftermarket cat back?

 

Made an account to add to this. I have the same issue with my 02 SR5. My old exhaust rusted out and so I replaced it, but kept the same O2 sensor and CEL came on after ~50 miles. So then I replaced the O2 sensor with a new denso but the CEL came back again after ~50 miles, again with a P0136. I also replaced my spark plugs which didn't seem too bad, just a little discolored. Truck runs fine, just seems a little rich.

I'm thinking there may be a leak either at the exhaust flange or at the O2 sensor mount. I'm not too confident in the gasket that came with my exhaust, it didn't seem like the right size (too thick and smaller than the ID of the relief cut in the flange on the Cat). Also the gasket for the O2 sensor doesn't seem to get sealed properly by the sensor cover? If I block the exhaust with a rag I can kind of hear some leaking at these locations, but I am not sure how to get a real solid seal. Any liquid gasket recommendations?

This is what I replaced the exhaust with:
http://www.autozone.com/emission-control-and-exhaust/muffler/bosal-muffler/631750/

 

I am running stock exhaust. Replaced the ECU and that didn't work. Now I have the abs light flashing too.

 

Just checking in to see if any of you guys had any luck eliminating the P0136 code. I'm getting that code now. It's been on for months apparently, maybe over a year. Didn't know until I went to do emissions and failed because the check engine light was burnt out...

Anyway, I'm hoping to solve this. I've battled this code for a long time. I've had dealerships and smaller automotive places work on it and it just doesn't go away. Any real solutions for this?

 

Found an exhaust leak at the downstream o2 sensor gasket. Repaired the leak and my truck is running fine with no CEL. Thanks for all the help!

 

Glad to hear you fixed it. I had this same code. Replaced downstream O2, CEL still on. The old gasket came off in pieces. Didn't seal the new one properly. Had to grind/wire brush the flange down till it was flat. Once it was sealed, light gone for good.

 

Just got this tonight. CEL came on, I can hear it when I get on the gas. It sounds like lifters chattering. I replaced the gasket between both cats but I think it’s the next one up stream.