Figured reach out for any tips.. 3 mechanics, dealer all spent few days cant pin point issue.

2012 gx460 base 95k
use bluetooth scanner with torque

3 months ago had p0430 code for bank1 s2.

• replaced both downstream 02
• immediately cleared the 430 with green check
• but then p0137 came up

• replaced the 3 exhaust gaskets, cleaned rust, they needed it but - error still there
• swapped 02's B1S2 at Lexus -error still there
• reset Computer, unplugged battery, drained it still there
• ran seafoam and catclean through vacuum - error still there but truck idles nicely
• had 2 garages including dealer run diags
• reset error clear it. it can come back right away within minute or startup and other days can drive 10-20min before it comes back.

mechanics tested the 02 good, connector and wires good but still error

truck runs fine, idles 550-650 , mpg are good been on long road trips no issues but the error.

Curious about cats and ECU.. and what i should look at next.
on torque when i hit the highway that has long uphill climb of a mile , there is no hesitation or lack of power for the SUV, it moves pretty well..

but here is what i saw on torque that concerned me, as i thought the cat should be reversed and higher temp on back side of the cat. mechanic also saw this and wsnt sure since both sides are exactly the same and no performance issues..
cat temp when idle
B1s1 is 1023F
B1S2 is 624F

accelerating on highway uphill climb after catclean
B1s1 ws 1511F
B1s2 is 1377F

after acceleration and just driving on highway
B1s1 1283F
B1s2 1079F
and bank 2 is identical in temps to B1 from idel thorugh accelleration

 

FYI, here is what that code points to:



There are lengthy diagnostics steps in the SM to track down the fault. It is strongly suggested to consult the SM if the tech has not already.

 

Thx its been at lexus dealer twice and a reputable toyota mechanic. We are starting to look at anything causing a pissible lean issue on bank 1. ..