02 Sensor/Scan tool

Good, now of these 3 sensors Sensor located in front manifold/exhaust pipe before catalyst Rear sensor, before catalyst Downstream sensor, after catalyst

Which one is sensor #1, 2 and 3? I suppose #1 is the front manifold?

Thanks,

John

Bank 1 sensor 1 (B1S1)

Bank 1 Sensor 2 (B1S2)

Bank1 Sensor3 (B1S3)

B1S1 and B1S2 should be switching rapidly between 100mv and 900mv once in closed loop. Since a properly operating catalytic convertor stores oxygen, B1S3 should hold fairly steady (usually high mv) with an occasional switch low to high or high to low as oxygen is burped off from the catalyst.

Yes, but which 02 sensor of the 3 relates to which sensor?

I mean, you've got 3 02 sensors, so which one do you pull if a given code goes off?

John

The individual O2 sensor codes will identify which sensor the code was stored for. i.e., P0131 translates to "Heated O2 sensor #1 circuit low voltage." P0134 translates to "Heated O2 sensor #1 insufficient activity." PO141 translates to "Heated O2 sensor #2 heater performance."

I believe I already covered this in my first reply.

ch one is sensor #1, 2 and 3? I suppose #1 is the front manifold?

Thank you Neil. So...

is the Bank 1 sensor 1 (B1S1)

is the Bank 1 Sensor 2 (B1S2)

and 3. Downstream sensor, after catalyst is the Bank1 Sensor3 (B1S3)

Sorry if I am a little slow on the uptake.

This evening I hooked up the autotap to the Tracker and fount the MIL code set to (I recall) P00135 which is 02Sensor Bank 1 Sensor 1 fault (I guess this sensor would be exposed to the most heat).

The strange thing is I logged the data from the car and it showed the

- O2 Sensor - Bank 1 Sensor 1 (mV) - was flipping back and forth while the - O2 Sensor - Bank 1 Sensor 2 (mV) - was steady at about 85 to 100 mv.

Another strange thing is that there are supposed to be 3 02 sensors in the car, but only 2 were listed on the Autotap.

I'll have time to crawl under the car and mess around with locating these, thanks very much for your answers.

John

First off, I think that site you mentioned is wrong - there seem to be only two O2 sensors on this vehicle, on either the 1.6L or 2.0L engine - one pre-catalyst in the manifold (HO2S 1) and one post-catalyst (HO2S 2). However, for some reason, on California vehicles, HO2S 2 is actually mounted before the catalyst below the exhaust manifold..

Secondly, code P0135 is HO2S Heater Performance - Sensor 1, this indicates either current draw on the sensor heater that is too low or too high, or incorrect output voltage on the circuit, with the heater on. Could be a bad sensor, or perhaps a blown fuse, bad wiring connection, etc.

Thanks Robert,

How confusing. Maybe I'll just go to the dealer and order them both.

John

The primary sensor will switch between about .1 and .9 volts. The secondary sensor will run mostly on the negative end. With the O2 failure the computer may be bypassing it and adjusting fuel based on a table in the code. This will keep the engine running reasonably normal and within emissions. The service manual has check procedures for checking it. If you are going to do your own service you should have one or check your local library for one. Information on O2 sensors can be found at