how can i check to see if an oxygen sensor is working or not?

 

If you had a bad oxygen sensor, I would think that the CEL would be on.

 

Using a DVOM, you can backprobe the signal and ground connections on the O2 sensor and monitor the voltage with the engine running. A properly functioning O2 sensor will ouptut a voltage that varies around .45 volts. As noted by WillieTD, if this voltage reads consistently above or below that .45 volts, it should cause the CEL to come on and the computer will put out a trouble code (O2 sensor always rich/lean, no HEGO switching detected, or the like). Other times the sensor is "switching" above and below .45 volts, but, for whatever reason, it is slow to respond or inaccurate in it's output. I saw one page that talked about testing this by artificially enriching/leaning the mixture using propane/vacuum leak to see if the O2 sensor can see the condition.
Hope that answers your question, without muddying the water too much.

 

i do have a cel. it indicates a lean condition on the left bank. i ask because i recently had the sensor changed because i got the cel. it had a broken wire, the new sensor didnt clear the problem.

 

I'm in sympathy with Bobs 93 X. I've been pouring over all the great info at this site for my CEL problem. I have a 91/4.0/2wd/XLT with 132,000 miles, recent plugs/wires/air filter, and got the dreaded Check Engine Light on the way to work one morning after about 10-15 minutes driving time. Accelration was poor, and gas milage is now out the window (130 miles to 16 gallons = 8 mpg!!!).

I bought the code reader, did a KOEO, and got "41" (02 lean). I replaced the 02, did a KOER, now I get "42" (02 rich). I reset the codes, cleaned the MAF and the Intake Air Temp sensor, checked the vaccum lines, air filter box and intake to throttle body. Did KOER test, still get "42" and even got "45" (DIS coil pack circuit failure). I reset the codes, changed the oil/filter and tranny fluid/filer, filled it with high octane fuel and added STP Super Injector cleaner. Still get "42" (no "45" repeat).

After all the above tries, the performance has improved slightly, but idle is still a bit rough, and pedal-to-floor acceleration is slow and hesitant, similar to "no advance" in the old days. Do 02 sensors go bad sitting on the parts store shelf? All help appreciated.

Bill K.

 

.....follow-up....Just went and did a KOEO for the fun of it:

KOEO (Current/Hard failure)
"11" System OK
KOEO (Continous Memory):
"41" (02 lean) and "45" (DIS Coil Pack circuit failure)

Guess I'm looking at the "no advance" problem a little closer now.

Bill K.

 

I have a simliar problem to Xplorerbilly but I only get code 41. I have changed the O2 sensor checked the vacuum and cussed a little. I got no clue but i could use a little advice.

 

The first standard test of an O2 sensor is measuring its output voltage, as I mentioned above. The second test with an O2 sensor code is to verify fuel pressure and fuel delivery. Also test/clean the mass air flow sensor.
When you're getting an O2 sensor code with a know good O2 sensor, then there is something wrong with the mixture (too much/little fuel, too much/little air).

 

One good way to check the o2 sensors is to use an OBD-II diagnostic device like the Auto X-Ray. I have one, and it can read live data from the vehicle as it's running, so you can actually see the voltage readouts without having to deal with backprobes. Make sure you get a reader that sends live data rather than just a code reader, though.

 

Dropped the Explorer off at the pro's. Result: # 5 cylinder is down to 50 psi, which means "valve job" ( $900.00~1000.00) I am told by friends that a valve job at 130,000 miles will most likely result in oil blowing past the piston rings due to the increased compression pressure caused by the newly seated valves.

Seems the most cost efficient outcome is a long block at $2200.00, turn key. Then all four power windows need the plastic gears replaced, the R34 AC that doesn't work, the coolant leak in the radiator, and the power steering pump which is leaking fluid (I fill it once a week). The transmission has a high pitched whine 30 seconds after start-up.

I doubt I'd get more than $1000.00 for her as she sits now. The body is straight and clean. Interior is very good. Do I build my Explorer back up for another 100,000 miles, or go purchase someone else's used set of troubles?

Bill K.

 

Well, when I was first on the market for a used explorer, I was going to go as cheap as possible, and the older the cheaper. But then I found out that 95 and up has wishbone suspension in the front. That sealed the deal for me. Let's face it...The truck is 12 years old, and for a little more you can get a nicer X.

 

franklin411: what year(s) explorer have you successfully read data with your Autoxray unit? At one time, I wanted to get one, but my research indicated to me that '93 Explorers were the first that had the capability of sending real time data to a scanner. If I get one, I don't want to pay $150+ for a glorified code reader.

Xporerbilly: I just went through the same thing with my '92 and I chose (A): build Explorer up for another 100K miles rather than purchase someone elses used set of troubles. I can't make your decision for you, but that's what I chose to do.

 

Yeah, you're right...My X is a 1996 and it's OBD-II compliant. I assume you need OBD-II to get live data from the computer. All the more reason to get a 1995 and up! With my 1989 Taurus, I didn't even have a code reader. Didn't need one. All I needed was a bent paper clip to jump the pins on the test socket and the light would flash...Those were the days!

 

I have an air/fuel meter code, and a too lean code. No o2 code but the I/M for the catylast is reading not ready. COuld that be a o2 problem?