[AJsCruiser]

I get a P0157 code and I've tried a bunch of things and I'm looking to see if someone has any ideas before I take my 2013 FJ with 130K miles to the Toyota repair shop.

I've done the following:
New spark plugs
New O2 & A/F sensors
Tried Cata-Clean
Tried O2 sensor spacers
Cleaned MAF sensor

None of this made any difference.

My diagnostics:
O2 sensors are working and I checked the wiring harness and I get the same readings on both banks so it's not a wiring issue.
Checked the temperature at the rear of the cats, the driver side was about 480 degrees and the passenger side was 510. Couldn't get a reading at the other end because of the heat shield.
When I look at the O2S2 B1 voltage it's around .7v to .8v The O2S2 B2 is at .04 when I'm idling. When I give it gas O2S2 B2 shoots up to .8v but then goes back down to .04v when I release the pedal.
When I look at the O2S1 B1 fuel trim its usually the same as O2S1 B2 but sometimes O2S1 B1 is double the value of B2.

The last thing I can think of is, is there a vacuum hose that could cause this? Or am I going to need a new cat?

 

[AJsCruiser]

You say you replaced all 4 exhaust gas sensors ... were these "OEM identical" sensors from Denso, or some aftermarket sensors?

Have you inspected the B2 downstream sensor connector for any contamination or corrosion of the connector contacts?

Do you run Top Tier gasoline?

Have you run a container or two of fuel injector cleaner through the tank?

Have you checked all exhaust system connections on the driver's side for any trace of leakage? With engine idling, have someone almost completely block the tail pipe and 'listen' around all the exhaust connections with a 18" long piece of 1/4" diameter copper or aluminum tubing connected to a couple feet of 1/4" vinyl tubing as an acoustic 'sniffer'.

There is a vacuum hose connected to the fuel pressure regulator located on the fuel rail towards the rear of the engine.

Here are the answers to the questions posed:

You say you replaced all 4 exhaust gas sensors ... were these "OEM identical" sensors from Denso, or some aftermarket sensors? All were Denso

Have you inspected the B2 downstream sensor connector for any contamination or corrosion of the connector contacts? Checked the connectors and they are good, clean, no shorts.

Do you run Top Tier gasoline? Yes from Costco or BP

Have you run a container or two of fuel injector cleaner through the tank? I've run Cataclean a few times.

Have you checked all exhaust system connections on the driver's side for any trace of leakage? With engine idling, have someone almost completely block the tail pipe and 'listen' around all the exhaust connections with a 18" long piece of 1/4" diameter copper or aluminum tubing connected to a couple feet of 1/4" vinyl tubing as an acoustic 'sniffer'.
Haven't tried this yet
There is a vacuum hose connected to the fuel pressure regulator located on the fuel rail towards the rear of the engine.
I will check these hoses.

 

[AJsCruiser]

FJtest, I disconnected a tube from the air cleaner that connects after the MAF sensor (seen in the pic circled in red) and the voltage for bank 1 and 2 downstream sensors were at about .04v. When I put it back on bank 1 went back up to .8v and bank 2 stayed at .04v. Does this tell you anything? BTW this isn't my truck, it's just for reference.