O2 Sensors

Hi,
New member and this is my first post here. Just bought the truck and I am pulling a P1135 code. Got the Denso part to replace the upstream sensor but as I was looking around, it looks like there should be a downstream sensor there as well, that is nowhere to be found. Can't imagine its supposed to be that way.

How can that be without dropping some other code? Or I am just missing something?

Thanks for any help/thoughts anyone can offer.

 

Welcome to the Forum!

The exciting things one might find one a 20 year old truck.

You have crawled under the truck and looked? Some times the bung is located you can not see the sensor from the right side.

Possible the truck has a device to send a counterfeit signal to the ECM saying the Cat or Cats are working.

 

Welcome to TacomaWorld
Previous owner may have removed the downstream sensor and installed an illegal O2 simulator to hide P0420
Catalytic converter efficiency below acceptable level.
Is there a straight pipe welded in where downstream sensor should be?

 

Yeah, I crawled under and looked and felt around. Didn't know they made such devices but I am at a loss otherwise. Thanks for the input.

 

Yes, there is a straight pipe but it didn't appear to be welded, thought it had flanges on it but I could be wrong. I didn't see any lose connector hanging free but maybe it was just tucked up out of the way. I'll have to crawl back under there again and do a deep dive.
Any idea where such a device may be located? Just curious now.

 

Welcome to TW....

 

As the harness for the second sensor goes down through the cab floor under or behind the right seat .

Things might be pulled up into the cab.

Happy hunting.

 

Look under the 1" rubber plug on bottom of passenger side floor panel. If you can't find the simulator there, pull the door sill rocker cover (3 screws) and look under carpet for wires and connector under seat area.

 

Thanks!

Seems to be tons of information here, may a bit too much as my head is approaching full capacity already.

 

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That back o2 sensor is a pig tail that plugs into the harness right there at the back of tranny...

 

Which goes up and over tranny to left side.....

 

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If you drive a little further around the mountain......

.....you'll see the 4 presidents.........