My question is it takes about 5 mins

Mechanic read cod PO136(indicates after cat O2 sensor)-replaced and code re-appeared within 10 mins.-He is now backtracking the wires which today I found out were good as well as the connectors/voltage-next he is going to replace the 02 sensor again with a different aftermarket brand to counteract a possible short inside the sensor-finally if that dosen't do the trick the ECu may need replacing-thats the game plan-could it be that a Hyundai needs to have a Hyundai sensor or is aftermarket OK?-Big difference in price. Please reply back this has us somewhat baffled me more than him, any advice much appreciated.

Thanks-I will pass it on-he did check all the wires for open circut and shorts-he relayed to me all was good/also voltage good but may not be reducing itself to 400 properly.

Hi Again

same issue-everything checked out-voltage right but it seems it doesn't whant to kick down from start uo(keeps running rich)-took out rear O2 sensor and very carboned up-also could a severely leaking(running) valve cover throw off the front O2 sensor(via the PVC valve) so the rear sensor misreads mixture as needing to be rich, so it never kicks down voltage required?

Thanks again for replying!

No the car is not burning oil at all-exaust is almost completely non-existant except for at start-up and then is can barely be seen. It seems very clean and runs very smooth, only leak is a very sustancial leak not from the head gasket-(compression test done and all is within specs)but leak from valve cover itself(gasket was replaced)-valve cove is on order and will be replaced

No-it takes about 15 mins. Till the car/sensor heats up

Yes-my local mechanic clears it by use of the scan tool at the garage at the computer-then the CEL comes back on in a few minutes-I'm stumped-have you ever heard of a CEL being so hard to diagnois-again the code reads PO136- could this possibly be a ghost code-hiding some other code?-I really appreciate your time and suggestion in attempting to walk me through this frustrating problem.

Hi

Thanks for all the help-I think I will just bite the bullet and take it to a dealer to diagnois due to the complexity-they have the state of the art diagnois machines. -With technology come a bigger price tag

I just took the car into a dealer of Hyundias and there were multiple problems-open terminals/bad hidden connector and an intermittent bad sender wire to the computor-its all fixed now and I just wanted to keep you updated

thanks again