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Discussion Starter · #1 ·
The passenger cat was stolen this past August off my 2006 Toyota Tundra TRD V8 with California Emissions. Insurance paid for a complete replacement including driverside cat and all new upstream and downstream O2 sensors.

As part of the install, my mechanic had to weld to the exhaust pipe on the passenger side to repair where the original had been cut off. Weld seems to be good and there are no noticeable exhaust leaks. Prior to the theft, I wasn't having either the P0420 or P0430 codes. Now, I get them consistently within 30 minutes of clearing the codes.

Here are the parts installed from Orielly's Auto Parts. OEM Magna flow bolt-on cats and Bosch sensors.
I confirmed with a Toyota tech that I got the correct cats installed same as what they would install at the dealership for a california emissions rig. We've cleaned the MAF sensor and spark plugs look good. Air filter is clean as well.

What am I missing? Before I start replacing brand new sensors, I just purchased the BlueDriver live scan ODBII sensor. Here are my readings:

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Discussion Starter · #4 ·
Thanks @tundrunk and @because_v8. Before I drop the cash on all new sensors, I decided to re-install the originals to see if that made a difference.

Prior to the catalytic converter being stolen, I had an O2 sensor code P0138 that I was trying to diagnose, so one of these "original" sensors is a denso O2 sensor installed downstream on bank 1. The rest are original to the truck as far as I can tell.

Now, I'm getting slightly different codes:

P0138 - O2 Sensor Circuit High Voltage Bank 1 Sensor 2
If I recall correctly, this is the code I got previous to the cats being stolen. It's confusing to me that I'm getting this from the newer denso sensor on Bank 1 driver side though. Perhaps pointing to a problem with the upstream AFR sensor on Bank 1?

P0430 - Catalyst System Efficiency Below Threshold Bank 2 (pending)
Bank 2 has all the original sensors on the passenger side. Is it possible that this code could be related to sensor issues on Bank 1?

The live readings I'm getting are quite a bit different now too. Anytime I let off the gas, both downstream sensor 2's drop to 0 volts, which it's my limited understanding is a good thing vs. the bosch sensors that wouldn't drop at all. Not sure what the spiky drops in both sensor 2's are about though. Any ideas?

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Thanks @tundrunk and @because_v8. Before I drop the cash on all new sensors, I decided to re-install the originals to see if that made a difference.

Prior to the catalytic converter being stolen, I had an O2 sensor code P0138 that I was trying to diagnose, so one of these "original" sensors is a denso O2 sensor installed downstream on bank 1. The rest are original to the truck as far as I can tell.

Now, I'm getting slightly different codes:

P0138 - O2 Sensor Circuit High Voltage Bank 1 Sensor 2
If I recall correctly, this is the code I got previous to the cats being stolen. It's confusing to me that I'm getting this from the newer denso sensor on Bank 1 driver side though. Perhaps pointing to a problem with the upstream AFR sensor on Bank 1?

P0430 - Catalyst System Efficiency Below Threshold Bank 2 (pending)
Bank 2 has all the original sensors on the passenger side. Is it possible that this code could be related to sensor issues on Bank 1?

The live readings I'm getting are quite a bit different now too. Anytime I let off the gas, both downstream sensor 2's drop to 0 volts, which it's my limited understanding is a good thing vs. the bosch sensors that wouldn't drop at all. Not sure what the spiky drops in both sensor 2's are about though. Any ideas?

View attachment 163033
So I had the same codes on my 06. P0138, p0158, p0420, p0430.
This was after installing new headers, cats, and dual exhaust. I replaced all four original 02 sensors with Denso and all the codes went away.
 

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Discussion Starter · #6 ·
So I had the same codes on my 06. P0138, p0158, p0420, p0430.
This was after installing new headers, cats, and dual exhaust. I replaced all four original 02 sensors with Denso and all the codes went away.
Just ordered all 4 new denso sensors, so that's my next step. Fingers crossed I get the same result!!
 

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Discussion Starter · #7 ·
Day 1 of driving on all Denso sensors for both upstream and downstream in the books. So far no codes pending! Will be taking a longer trip soon, but fingers crossed that the issue has been resolved! Appreciate the advice. Now to see if the parts store will take these Bosch sensors back...
 
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