reneramos

I have read most of the threads and watched the utube video about the fluctuation of the O2 sensors by OBDII, and the temperature pre and post cat at operating temperature mentioning the outlet temp. being higher. I used a laser tester and all 3 cats the outlet temp was lower than the inlet temp. Maybe I miss understood something. I still need to do the OBDII check. However, I am still confused. Will y'all give me some direction as a do it yourselfer, meaning cash poor.

DMPesso

a 420 is an exhaust leak or a O2 sensor guaranteed. First check for leaks, if none replace the o2 sensors in bank 1..

NVRLFT

Do you have a scanner that will graph o2 readings?

reneramos

I may use a scope from work. Or ask the auto part store if their OBCII wil monitor realtime voltage. The are the temperature readings with a laser.

Bank 1 cat pre 472deg
Bank 1 cat exi 310 deg
Bank 2 cat pre 374
Bank 2 cat exi 262
Back 274 deg pre
Back 190 deg back

reneramos

After changing the exhaust manifold gasket, the check eng light for Bank1 came back. So I had advice to take it to the shop. They replaced both cats and removed the 3rd, "since its not being monitored", he said.
just 10 miles down the road Bank 2 sensor failure code came in. I was able to break is loose however, it might be easier to remove the manifold instead of making a 1/8th of a turn when I can with a 22mm wrench. I should of had them change it when installing the new cats!