Originally Posted by Rav4tech
I didn't see where it mentioned 'modern' car.
It does state "if the circuit is not complete, the computer picks up a steady 0.45 volts." Possibly indicating if the O2 sensor was unplugged the computer would see .45volts from somewhere, not the O2 sensor.
While describing testing for the .45V he uses the term "most late model cars"
in the body of the article and starts by saying "These procedures are only for self powered conventional (one-wire) sensors. Some very new cars are using a different style sensor that is powered."
Since the last turbo Regal on his forum was made in the late 80s and one-wire sensors are long gone, what I'm saying is altho some of the info still applies to 14.7 narrowband sensors, don't expect to find the .45V readiness test signal anywhere on a four-wire wideband sensor.
I was just hoping someone would go out to their Rav4, unplug the rear O2 connector and check the voltages from the vehicles connector, key on of course.
Would be nice but you do realize that's it's 20 degrees in the northern states and most of our members wouldn't have a clue how to do what you suggest.
Regarding the 3.3volts for the A/F sensor.
Go to Automotive Training and Resource Site
click "Technical Articles" in the left column. Then scroll down and click on article #37 regarding Oxygen Air/Fuel sensors. Read the first 11 pages. The Air/Fuel ratio operation is described beginning on page 6, referencing the 3.3 volts.
Excellent article and I see the confusion. He refers to what I'd call a narrowband sensor that's used to set the engine's AFR
as an "oxygen" sensor, and what I call a wideband one that's used to read the engine's AFR
after the cat, as an A/F (AFR) sensor. That's where you're getting the 3.3V which is correct. And altho I believe the nomenclature "oxygen" and "A/F" sensors may be common in the industry, I still prefer narrowband and wideband to distinguish them since technically they both measure oxygen content just in different ranges. But I'll have to remember their terminology when talking to automotive techs just like I do keeping track of black and white in electrical or electronic wiring.
Also note: at the bottom of each page it indicates copyright by Toyota Motor Sales.
Sure would like to have dates for both articles. I guess the Regal forum one is about 1990; the Toyota, 1995.
The wideband AFR sensors my dyno uses to get it's fuel graphs are five-wire. The fifth wire is for a built-in calibration resistor to compensate for manufacturing tolerances. Five-wire sensors have been used on some "modern" cars for ten years.