Question about 1999 Lexus ES 300
Usually the ecu never gives a code on a catalytic converter, but rather the o2 sensors. it seems much more logical that it is the o2 sensors than the cat. fixing the problem usually makes the light go away but not always, so resetting the computer is adviced. also, resetting the ecu would not change the way the car runs because it should be working normally, which means, if its running rich, the problem still exists. like i said, most likely it is the o2 sensors, especially because they go out fairly commonly. hope this helps, good luck.
p.s., if the muffler did get replaced, need high flow o2 sensors, but that depends on the muffler. also, i posted alink to a lexus forum so when ever you have problems with your car, you can ask there:
Posted on May 19, 2011
Hi, a car that's running rich can also cause this code to set. You might want to check your fuel pressure regulator for a torn diaphragm. The regulator is on top of the engine connected to the fuel rail and looks like the picture below. Pull the vacuum hose off the regulator and plug the hose with a golf tee. Then start the car and watch for any fuel that spits out of the vacuum port of the regulator. This indicates a torn diaphragm. Please let me know if you have questions, and thanks for using Fixya.
Posted on May 19, 2011
I have a llexus wirth this problem also and found the air cleaner hoses were broken also fuel pressure regulator screw was all the way out I replace all this parts and reset the check engine light test drove the vehicle and dint found any other problems sofar good luck hope this will help since every vehicle is different test all related parts and functions is advise
Posted on Jul 04, 2013
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Posted on Jan 02, 2017
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