surfRider

Could someone point out the test port connections for checking the 02 pre-cat sensors?

Thank you

Yamae

I hope the link below may help you some although it is for a JDM Celsior UCF10 of early version and things are mostly written in Japanese.
http://sekainokurumakara.cocolog-nif.../o23-75a3.html

I think I need to explain important part in English at least for you. But I have to go out now and I will be doing it after coming back.

surfRider

Thank you, please take your time. It is holiday time.

I did find the O1 and O2 ports but not sure if the other connection should be ground or another port. It appears in the Japanese article it might be the E1 port but I will wait for your explanation.

Thank you,

Yamae

The generated voltage by the O2 sensors can be monitored at OX1 and OX2 at the DIAG connector indicated by the drawing below.

The red one is coming from Bank1 O2 sensor and the one indicated OX2 below is from Bank2.

When you measure the voltage, you need to warm up the engine and then keep the engine rpm 2000rpm and connect the probes of your voltage meter to OX1/OX2 and E1.
The voltage has to swing at least 0.35V to 0.7V acrossing 0.45V. A good O2 sensor and a good engine usually swings between 0.1V to 0.9V.

You also can confirm measuring the feed back voltage VF１/VF2. It should be 2.5±1.3V（ranging 1.2～3.8V）.

surfRider

Per Yamae's O2 sensor test he just posted, both sensors show good readings, 0.40-0.60 volts.

Yamae

A good reading range is between less than 0.35V to higher than 0.7V. Your result is a bit less or should I say narrower. In other words the low side should be less than 0.35V and the high side should be higher than 0.7V. But a precise measurement needs an oscilloscope though. An aged O2 sensor usually can't generate enough voltage.

I have experienced several cars that turned on the engine check light just once in a while. I mean the car is usually OK without turning on the light but it turns on when going down/up long hill or just running a plain flat road for a long time. These cars were all fixed by changing the O2 sensor. Those aged sensors did not generate the voltage enough. The high side was less than 0.65V.

The page below may help you to know more.
http://www.mxcom.net/hearst/motor/mo...tor_eNews.html

surfRider

I will run the tests again today as the readings were jumping quite a bit. I basically averaged the low and high and did not realize the range is so sensitive. I will also check on just changing out the sensors as the price is not high just the time to put them in hard to schedule. I will post back as I am sure others appreciate this thread as much as I do. Thank you

I finished reading the article supplied and from that information I can see why a scope is the proper tool for testing the O2 sensors. I think my volt meters may not be accurate or quick enough to give good readings but will do the testing again.

surfRider

After several tests I was not able to get satisfactory readings. Both of my voltmeters would jump from no voltage to 11+ volts but not consistent enough to pick a range. I think the next best thing to do is replace at least one sensor and test. If nothing improves maybe swap the sensor to the second side, if still nothing then get a second sensor and (keeping my fingers crossed) replace both.

surfRider

Well it appears that is the solution. I changed out both sensors and as yet the ECL has not come on. The car still runs rough after all of the other fixes but at least the light will not come on during the smog test. Thank you for the suggestion and perhaps someone else will learn from this thread.