Changing upstream and downstream O2 sensors

[east_stingray]

General consensus is that you should change 4-lead O2 sensors about every 80k miles. When I started to do this, I looked but could not find a writeup on how to go about it, so here goes.

Disclaimer: If you somehow screw this up and break something, it's not my fault. If an earthquake knocks your car off the jack and kills you, it's not my fault. If this causes you to start getting incredible gas mileage, you can blame that on me.

First:

Decide which type of sensors you are going to buy. I bought Bosch universal sensors. Bosch also makes a sensor specific to the celica. The difference is that the celi-specific sensor comes pre-wired to the connector that plugs into the celi's wiring harness. If you get the unviersal, you have to cut the connector off of the stock sensor and splice the four wires into the new sensor. Here's the kicker... the Advance Auto here charges $70 for the universal sensor and $170 for the specific one. I'll splice 4 wires for $100, thanks. Oh, and to clarify, you will need TWO sensors... the '00 GT uses the same sensor upstream and downstream.


Next:

Locate your O2 sensors. The '00 GT has two of them; one in front of the cat (upstream) and one behind the cat (downstream). I'm operating on the assumption that all of the 7th gen celicas are set up the same way.



This picture shows the upstream sensor (looks like a spark plug with wires hanging out).



This picture shows the hole where the downstream sensor lives.

I would reccomend removing both sensors before doing any other part of the process, as you might find that they are nearly impossible to remove. The front one came out ok, but I had to use a gun penetrating solvent to break the rear one loose. You will need a 22mm box-end wrench for these. On the safety side, Never get under a jacked-up vehicle that is not on jack stands unless you want a closed casket funeral TOMORROW!. It's also a good idea to set your e-brake and chock the back wheels before jacking.


Once you've removed both sensors, unplug their connectors from the wiring harness. The connectors are located under the carpet near where the passenger's left foot would be:



Run the connectors down through the frame (you'll have to push out the gaskets). Now take the removed sensors and new sensors to a clean, well-lighted area to do your wiring.

This part highly depends on the wiring instructions of the sensor you purchased. The two black wires on the stock celica sensors are the heater wires, and the polarity of these does not matter. On the bosch sensors, these are connected to the white wires. The other two wires are matched based on the matching table provided in the instructions.




A few things I forgot to do:

Don't forget to thread your gaskets back on before wiring the new sensor. I forgot to do this and there is no way to fix it short of cutting it apart and wiring it back up again. As you can see in the above picture of the front sensor, I also forgot to thread the insulation/protecting sleeve back onto the sensor's wires before wiring it to the connector.

Good luck, I hope this helps, and ENJOY your increased gas mileage!

[anvle]

awesome writeup... thanks alot...

[ek9max]

do yo uhave hte model # on teh sensors?

[reddragon]

Does it really matter if the computer is saying I need o2 sensor bank1? Are they both the same bank1 and bank2? Which would be bank 1? Thanks

[anvle]

hope this helps: http://www.newcelica.org/forums/show...ighlight=bank1

[reddragon]

Originally Posted by anvle

hope this helps: http://www.newcelica.org/forums/show...ighlight=bank1

Thanks for the info.

[JCMiller]

So yesterday I got P0141 -

H02S 12 heater condition (Heated Oxygen Sensor Bank 1 Sensor 2)

I figure its an 8 year old car, 67k miles it is time to change them instead of fussing with them to prolong their use. Went to advanced auto and purchased Denso Oxygen Sensor Part # 112479 for $160.99. I figured this was a better deal since Toyota sold the same one for $190.99 + shipping. I didn't go with Bosch because they were $40.00 more expensive at AA and $50.00 more expensive at the dealership.

Did I buy the wrong part? Since you said I shouldn't be spending more then $100.00 I feel jipped. Do you have a specific company you prefer to buy from online? Thanks.

[deltaB]

Originally Posted by JCMiller

...I feel jipped...

You should.
I got a toyota one for the front from conicelli last year for 103.27 shipped.
ΔB

>>Order Status Details Order Date: 2/15/07 8:51 PM
Description Qty Price Core Price Total Price
Collision Catalog - 2000 - Toyota - Celica
Emission system, Emission components, Oxygen sensor, Front, Gt-s 1 $105.91 $0.00 $105.91
Status: Sent
Sub Total $105.91
Discount Applied: -$10.59
New Sub Total: $95.32
Tax $0.00
Shipping $7.95
Handling Fee $0.00
Total $103.27

[JCMiller]

Maybe front sensors are just cheaper then the back one?

[deltaB]

>>Item Number MSRP Core Price Price
>>8946520710 $156.84 $0.00 $119.20
>>Electrical - Powertrain control - Oxygen sensor
>>Oxygen sensor, celica, gt-s, rear 2000 - 2003

>>8946520700 $139.25 $0.00 $105.83
>>Electrical - Powertrain control - Oxygen sensor
>>Oxygen sensor, celica, gt-s, front 2000 - 2003

About $15. The cable is a little longer. Must be expensive wire.

BTW, it was the heater that broke in mine too.
ΔB

[JCMiller]

I'm not very handy with repairing things on cars, but I plan to do this myself. Seems very easy, but are there any precautions I need to know?

[deltaB]

Originally Posted by JCMiller

I'm not very handy with repairing things on cars, but I plan to do this myself. Seems very easy, but are there any precautions I need to know?

Not really.
I either used my foot or a jack on the wrench to get it started. After that it was a piece of cake. I didn't check the sensor before I ordered the new one. I was glad the heater measured open-circuit after I took it out. I didn't want to pay for the sensor just to find out I really had a wiring problem or something like that.
ΔB

[Pansolo]

Found celica specific sng sensors on partsgeek. com for a great price. Wires will be a tad short so screw the sensors in first. You will have to detach the female ends from the car (twist and pull) in order to reach the new sensors.