O2 sensor test in a 94 (1 Viewer)

[rc51kid]

Need some advice on testing my O2s on my 94. The FSM says to test the resistance between two prongs on the side near the "clip". I have a multimeter and set it to "OHM X1K". I have a resister that should be 4.7k. When test it it reads between the 4-5. So it looks right to me. When i test my O2 it reads "0",the needle swings all the way to the end of the meter. Both sensors do the same thing. Am i doing something wrong or are the O2s bad?

PS my sensors might not be 68 degrees right now. The exhaust is slightly warm to the touch but not hot at all and it is probably about 55 degrees out.

 

[Timpanogos Slim]

I hope you are doing something wrong? I forget what the resistance of the o2 sensor is supposed to be, but 0 would indicate that you meter has a funny way of saying the reading is out of range or the o2 sensors are shorted out.

sadly the o2 sensors for 93-94 are different, and expensive.

try testing other combinations of pins, and try other range settings.

 

[Brentbba]

Some time ago, I used the FSM to trace down a fault code and it involved testing like you are describing. Tests on the sensors themselves showed fine as did every other test I ran per the FSM. Long story short, I replaced the sensors and all was fine!

 

[rc51kid]

Some time ago, I used the FSM to trace down a fault code and it involved testing like you are describing. Tests on the sensors themselves showed fine as did every other test I ran per the FSM. Long story short, I replaced the sensors and all was fine!

The other question is, do these go bad with out testing bad or throwing a code? I keep failing emissions. Runs good but crappy (12MPG) MPG no engine codes. It is failing emission from too much CO (rich) but no engine codes.

 

[Timpanogos Slim]

12mpg is sort of normal for a '94?

 

[rc51kid]

12mpg is sort of normal for a '94?

Sort of. If that is all i gt i am OK with it. But when i bought it i was getting CEL "rich mixture" and got 12 MPG on the highway home for 120 miles at 60 MPH. I figure at 60, it should do a little better.

 

[Timpanogos Slim]

highest i've seen in mine was 14 on the highway.

If you measured the wrong pins on the connector, that could have been the heating element, which would have very low resistance.

try the other two.

 

[rc51kid]

i had one other question or thought about the O2. IF the truck is running rich,as indicated by the high CO, why arent the O2 sensors fixing it?I mean if something os bad in the engine side,adding too much fuel. i would think the O2 would see this and lean the system.

 

[Brentbba]

I hate to suggest it, but change the sensors. Expensive but may be necessary.

 

[Cruiser Ed]

Hey rc51kid

I failed Aircare in my 97 LX450 here in Vancouver, Canada a couple months ago and parked it till last week. I had no engine codes. The engine I believe is a little different but here's what I did to pass:

Both O2 sensors. Denso brand.
Coolant temperature sensor
Oil change
Put my car in "PWR" mode unlike before

Here where my results


I think my cats or EGR need replacing to get the NOX down.

 

[rc51kid]

Hey rc51kid

I failed Aircare in my 97 LX450 here in Vancouver, Canada a couple months ago and parked it till last week. I had no engine codes. The engine I believe is a little different but here's what I did to pass:

Both O2 sensors. Denso brand.
Coolant temperature sensor
Oil change
Put my car in "PWR" mode unlike before

Here where my results
http://s203.photobucket.com/user/livingdead_Ed/media/Aircare_zps51600d3f.jpg.html

I think my cats or EGR need replacing to get the NOX down.

That is really good advice. I was actually thinking about the temp sensor. If it was not reading accurately then the engine would be adjusting the mixture for for a different temp engine. Possibly thinking that the engine is cold and making it rich. Was your temp guage working for you if your temp sensor was bad? Does the one sensor control both the dash temp gauge and "talk" to the ECU for mixture?

 

[Cruiser Ed]

My temp gauge was working. I replaced it because someone else here had an emissions problem and he traced it down to the coolant sensor and it was only 15 bucks so why not...part of baseline maintenance i guess. Also, i bought it from RockAuto and wanted to get the most out of my shipping fees buy buying a bunch of stuff.

I'm unsure if the temp gauge and the ecu use the same sensor.

From my experience with emissions here in Vancouver, o2 sensors, cats, timing and egr valve fixed the fails that I remember.

 

[rc51kid]

I looked it up, the dash reads off of a different sending unit.

 

[rc51kid]

I just ordered both O2 sensors (kit), the temp sensor and some unrelated interior trim clips from Sam. We will see if this straightens things out.

 

[SoularVibe]

Did it straighten things out?

Currently having same issue .. high CO @ emissions . buuuuut ..... filled up tonight and pulled 15 mpg (300 miles, 19.8gal .. fuel warning light had just came on as I pulled up to pump... 3.4 gal left I think .... anyway , an update would be great

 

[TX FJ80]

I just ordered both O2 sensors (kit), the temp sensor and some unrelated interior trim clips from Sam. We will see if this straightens things out.

Who did you buy this "kit" from? I am in need of the same thing, just to get a baseline to clear DTC 25/26 on my '94.

 

[OGBeno]

Who did you buy this "kit" from? I am in need of the same thing, just to get a baseline to clear DTC 25/26 on my '94.

You need 89465-60110: 2 sensors, 2 gaskets and 4 nuts.

 

[Brentbba]

You need 89465-60110: 2 sensors, 2 gaskets and 4 nuts.

...and depending on where your truck lived before Dallas, if it did, some WD-40!

 

[TX FJ80]

Thanks beno. What about the temp sender as well? I had never considered that the dash and the ECU read temp from two different sending units - but this issue only pops up when cold as hell outside.

I'm gonna replace it while I'm at it. Anyone on here wanna sell me all this?

 

[OGBeno]

Sensor for the dash gauge: 83420-16040

Sensor for the ECU/EFI system: 89422-35010. Gasket: 90430-12005