New User and I need your advice P0125, P0130, P0420

[ManfredN]

Ok gurus I need your advice on a 2002 Corolla manufactured in late 2000. I have 157,000 miles on it.

My Car's computer keeps spitting the following codes at me. P0125, P0130, P0420. The most common of the codes is P0125. The P0420 has not shown up in a while (if I remember right). The P0130 was a brand new one that popped up today. When these codes strike I get about 4 mpg worse.

I have a newish catalytic converter on it and I have also cleaned the MAF. After doing some research I have come to the conclusion that my front O2 sensor needs to be replaced.

Am I right or wrong?

[bail_w]

Since your corolla has 157k, have you done any maintenance on it? I say you should replace the front o2 sensor and spark plugs.

P0130 and P0420 most likely caused by the o2 sensors reading are close to same. If replacing the front o2 sensor doesn't fix it, look up o2 sensor defouler.

[sam333]

+1
The bad milage makes sense with a 125 ,the computer is not seeing rich signal from your o2 sensor ( computer adds more fuel) . 130 your o2 signal is not swinging as high or as low as it should( could look like the rear o2 signal( 420).

[ManfredN]

I am now getting a P0133 code. I think it is time for a new o2 sensor. thanks guys!

[ManfredN]

Went to my mechanic and he looked under the hood. Guess what he found and showed me! Oil covering the 02 sensor!

[ManfredN]

Well after the mechanic told me about the issues I decided to bite the bullet and get it fixed.

Here is what they did.

Replaced Valve Cover Gasket and tube seals: cleaned PCV valve (completely clogged), replaced front o2 sensor.

Complete oil change

Total cost for labor and all parts needed. 307.33