Location of Post Converter Oxygen Sensor

[PaulSandrav4]

I just ran a scan on my 1998 rav4. Trouble code PO136 popped up. The code is
explained as "Post Convertor Oxygen Sensor or circuit fault. Do this mean I need
the upstream sensor or the downstream sensor and exactly where is the Post
Convertor Oxygen Sensor located on the 1998 Rav4. I have a 4 cylinder 4 wheel
drive. Pictures would help.

Thanks

[RAVRaver56]

I have the same problem so I am bumping this post. On my 98 RAV4, 4WD manual, there is a sensor by the catalytic converter, is that the Bank 1 Sensor 2? There is a sensor in the down pipe from the exhaust manifold also, is that Bank 1 Sensor 1? I have a Haynes manual and the drawings look nothing like what is on the car.
Also, I bought a Bosch Universal O2 sensor. They give you the wiring for the sensor and for several makes and model cars, but not Toyota. Does anyone know which wires are the heater and which the sensor?

[calgaryrav4]

Right out of the toyota shop manual

"sensor 2 refers to the sensor farther away from the engine body"

Not the clearest description...

I guess that is the one after the cat as it would be the farthest away from the engine

[mensajero]

I'm going to relate to my specific 3SFE engine. But I guess the principle are the same.

On my exhaust manifold I saw two O2 sensors. After reading a little the two sensor work together. The first sensor monitors the A/F Ratio. The second one sees that the first one is working. When I installed my header, the same applied. They must not be exchange from their OEM position. It doesn't matter how far one is from the other in your exhaust system.

They both must be installed or the Check Engine light will come on and your wallet will feel the pain at the gas pump. So much that you can see the fuel gauge needle drop as it eats up gas.

[2001SL2]

^ That didn't answer the question though


POST converter means after, so it's the one after the cat converter, towards the back of the vehicle. That sensor is a regular O2 sensor that makes sure the cat converter is doing its job. THAT"S bank 1 sensor 2

The sensor in the exhaust manifold regulates the fuel mixture. That's bank 1 sensor 1. In California versions that sensor is a more accurate and more expensive Air/Fuel ratio sensor, not a regular O2 sensor.


Hope that helped

[RAVRaver56]

Thanks guys, now I know which one to change.

[calgaryrav4]

Originally Posted by mensajero

The second one sees that the first one is working.

this is not true for the bank1 sensor2 (b1s2). It can't really read what the bank1 sensor1 (b1s1) is doing because the A/F ratio is changed in the catalytic converter.

The ECM checks the bank1 sensor1 (b1s1) two ways.

Running at a certain fuel trim % there is a approximate value that the (b1s1) should be at.
Or if it changes the fuel trim % (+/-) the b1s1 sensor value should change accordingly.
If it is out of range you get a CEL. The ecm will then default to a rich fuel trim (same as cold start as the b1s1 is out of range during cold start but without the CEL )

The ecm uses the b1s2 for for monitoring the catalytic converter (cat) efficiency by comparing b1s1 values with the after cat b1s2 sensor value.

Originally Posted by mesajero

It doesn't matter how far one is from the other in your exhaust system.

I think it matters somewhat , but more based on the cat placement (I could be wrong. I have never read any info on cat placement in relation to its performance but I'm asmuming that they put it there for a reason). The cat should be placed as close to the original spot as possible (to help keep warming time low) with the sensor as close to the factory distance from the cat as possible.

[RAVRaver56]

Well, it went in like butta. One of the few things I have done on the RAV that were easy to do. So many components appear to have been assembled onto the engine before it was put in the car, with no regard for easy servicing. Several times I have had to throw in the towel and take it to the dealer for service.
Anyway, I cleared the code and drove about 15 miles with it so far with no problem. Thanks again.