wesleyzhere

first p0157 came on then a 2 days later p0420 idles a little rough but runs gfood and nbettert milage

oo7spy

Why no search?

wesleyzhere

new to this stuff not sure what you mean i think i did try tyo search

oo7spy

Google can tell you what the codes mean. P04## are common codes brought up on this site. I guess I assumed you started this thread with a question in mind, and so I wondered why you didn't search first. Now I'm just wondering if you came to tell your story. If so, cool.

Getterdun

The P0157 is often due to a faulty O2 sensor at the base of the catalytic converter at the rear of the engine. The P0420 alone is most likely due to a problem with the rear catalytic converter. I'm currently working on a 2005 RL with this code. Since you got the P0157 first, I would replace the O2 sensor and hope it clears the P0420 code too.