Problem Removing Upstream O2 Sensor - Corolland: the Toyota Corolla Forums

2000 Corolla CE

Having problem passing emissions. Both 02 sensors are giving 'not ready' to emissions test, so its time to R&R them.

I've researched the procedures, seems straightforward, except for the downstream sensor. Because it appears the

2nd sensor was added after the design of the model. This is the one that has the electric connector under the carpet

inside the cabin, and requires removal of the passenger seat to pull up the carpet to gain access to the connector.

The consensus of other mechs seems to be it's easier just to cut the wires going to the sensor, and splice the new

sensor in. ( Now i understand why the Denso sensor without the electrical connector are popular on this model ).

So, i spent the good part of the day soaking both down both sensors with PB blaster, and driving the car, to maximize

penetration. Decided to R&R the upstram first, since it's accessable from the top of the engine bay.

There are 2 12mm nuts that hold the sensor bracket into the exhause manifold. Remove these 2 nuts and the sensor and plate should just come out. Wrong!

Of course, one of the nuts was severely corroded, and actually rounded using a 12mm. After much effort, I was able to remove it with an 11mm ( another time i wish i had a $100 metwrench socket set ).

After getting both nuts off, the plate and sensor did start to come off, but cannot be removed, because, i discovered, the exhause manifold/Pre-cat tube flange bolt head is the way! The bolt head on the cat side of the flange protrudes about 1/8" below the top of the plate, making it impossible to remove the plate/sensor!

So, I thought I'd retighten the plate and use my (3/4) 22mm o2 socket to remove the sensor from the backing plate. But

the socket is too big for the OEM sensor!

So, my choices at this point are:

I will either have to get the correct OEM 02 sensor socket (SST?), or take it to my mech with his lift and air tool to remove the 14mm flange bolt, and maybe have him replace it with a shorter bolt, so future R&R wont be a problem.

This situation seems very strange, as this problem only appears on the 2000 model. This video below show someone removing the up sensor on a 2001 with ease! Perhaps the factory realized their mistake and started using shorter flange bolts on the cat side? Hmm

Mine is a 2002 and it sounds very similar to your setup. I think it has more to do with what parts availability (batch) was in assembly at the time. Mine were so corroded, I just ended up, using a cutoff tool and dealing with the aftermath later. I did everything I could to keep the existing connector. Not a high data rate through the connector, but I didn't want to chance signal reflections from a poor connection after the fact.

This might be one of those things you let a shop deal with - they all have the tools to deal with those sensors + they can put it on the lift, which helps tremendously.

well, about 6 hrs after i posted this, i found an EASY solution. I was looking at the comments on a youtube video above, and found someone had the same problem. He claimed he pushed on the exhaust pipe ( toward the pass side ), and was able to free the bracket. I tried it on mine, and Viola! I used a 2 ft length of 2x2 wood and tugged on the sensor wire, while using shoulder pressure on the wood to move the pipe..The bracket and sensor fell out....I love simple and CHEAP solutions. default_smile

Nice!