Which oxygen sensor is which?

[corboto]

I'm getting a diagnostic code 21 in my 89 FJ62 and have searched around Mud but haven't found anything that definitively states which O2 sensor is for which code. Code 28 also applies to an oxygen sensor. So is code 21 for the sensor that is nearest to the wheel well or for the one by the transmission linkage?

I plan on swapping both out soon but want to change the bad one now. Thanks a lot.

 

[WalkerTech]

Corboto, I am a product specialist with Walker Products, a manufacturer and worldwide distributor of oxygen sensors. Code 21 refers to your main O2, and Code 28 refers to your No. 2 sensor. The link below can help you determine which is which. Oxygen Sensor Catalog 2012

 

[corboto]

Thanks for the reply. I'll take a look at your link.

Sent from my Galaxy Nexus using IH8MUD

 

[corboto]

Corboto, I am a product specialist with Walker Products, a manufacturer and worldwide distributor of oxygen sensors. Code 21 refers to your main O2, and Code 28 refers to your No. 2 sensor. The link below can help you determine which is which. Oxygen Sensor Catalog 2012

This appears to be generic information (no offense) unless I've missed something. The 62's have both O2 sensors before the cats and none (that I'm aware of) after the cats. Thanks for the link though.

 

[disassociative]

I happen to have my wiring harness apart and happen to be a little OCD about wiring...

Here is the upstream (US) sensor



and the downstream (DS) one.



I wasn't sure which was which either, so I made labels...here is the troubleshoot for reference.



I'll follow up in a moment with my records about wire ID, I can't stand swype-ing detailed info...

 

[disassociative]

The labels are a little confusing because I made a couple modifications for my ease of reference. The wires labelled "E1(GRND)" are ground wires that correspond with the ECU terminal E1. The ones that are labeled "PWR" correspond with the ECU terminal +B.

An easy way to tell at either end (ECU or connector) is by wire color, because Toyota kept it simple:

OX1 = dk blue, 2x white stripe
OX2 = solid yellow
HT1 = solid gray
HT2 = solid orange

On my 88 FJ62, the "DS" sensor was the one with somewhat heavier wire shielding. It branched off of the wiring harness closer to the ECU and the female side of the connector has a plug that secures it to the transmission to hold it out of the way from being entangled by the A440 shift lever mechanism.

The "US" connector branched off just before the rest of the harness tracks along the fuel rail. It runs straight down from this position to plug into the exhaust pipe that comes off of the 4,5,6 cylinders...I am only 85% sure of the exhaust pipe/cylinder relationship, FYI.

Hope this helps. Here is the last of my records...just in case you want to test continuity and compare charts

 

[disassociative]

Forgot to show the most relevant picture...



The one closer to the midline is what I call downstream (DS) and appears to be for the 4,5,6 cylinders.

 

[Dave1x1]

Since I'm about to have the shop reweld my Slee bungs and re-attach the sensors and I didn't mark them beforehand, I went back and re-read your post. Only thing I'm not sure about is in the last 2 posts you mentioned the "US" sensor being attached to cylinders 4,5,6 and then in the last post you say "DS". Were you able to determine which sensor went to each cylinder?

Thanks!

 

[disassociative]

Since I'm about to have the shop reweld my Slee bungs and re-attach the sensors and I didn't mark them beforehand, I went back and re-read your post. Only thing I'm not sure about is in the last 2 posts you mentioned the "US" sensor being attached to cylinders 4,5,6 and then in the last post you say "DS". Were you able to determine which sensor went to each cylinder?

Thanks!

The one I call 'DS' is for cylinders 4,5,6. Sorry for the confusion.