2006 GS300 AWD. Was getting a exhaust rumble coming from under the car so took into shop and they said mid-pipe needed to be replaced (cats were going out). There were no engine codes before replacing the mid-pipe. Bought a new mid-pipe and (2) new denso oem downstream o2 sensors. Shop installed the new mid-pipe but said they couldn't do the o2 sensors. Next day check engine came on with p0420 and p0430. Thought it might be the o2 sensors so I installed the new o2 sensors and cleared the DTC. Came back with the same issue. Here is the techstream data. I'm not sure what is going on. My thought is there is an exhaust leak in one of the seals/gaskets of the mid-pipe but I don't know what the values/fails mean. Can anyone help? Thank you.

 

Following this thread...

 

When you say "New mid-pipe" what is the part number they sold you and had them install?

 

A whole new Y-pipe or mid-pipe bolt on with (2) new cats.

https://mufflerexpress.com/collectio...verter-3-0l-v6

2-year Option.

 

Here is more detail on each FAIL with a description from techstream. I'm hoping a Toyota or Lexus tech. can pinpoint what the issue is.



Catalyst Efficiency

O2LENB1B = RrO2 sensor locus length of Bank1 catalyst for "B" area

O2LENB2B = RrO2 sensor locus length of Bank2 catalyst for "B" area



O2 Sensor

.45V MOR B1S2=Maximum time while sensor voltage exceeded .45V continuously for Bank1 Sensor2

.45V MOR B2S2=Maximum time while sensor voltage exceeded .45V continuously for Bank2 Sensor2



F/B Comp B1S2=Percentage of time when sub-feedback compensation factor remained greater than or equal to .05V for Bank1 Sensor2

F/B Comp B2S2=Percentage of time when sub-feedback compensation factor remained greater than or equal to .05V for Bank2 Sensor2



Area 4 B1S2=Percentage of the time when sensor voltage was .7V or greater for Bank1 Sensor2

Area 4 B2S2=Percentage of the time when sensor voltage was .7V or greater for Bank2 Sensor2

 

currently having the same issue and I got new sensors, headers, mid pip and Tanabe Medallion Axle back.

I was told the O2 may need a spacer but I'm not sure how that would do anything. I am aware of the carbon issue so we'll see how this plays out.