O2 Sensor...Test?

[Richard Cooper]

Does anyone know if there is a way to test your oxygen sensor? In the book it tells me all about it, but not how to test it. Also, the book shows a two wire sensor, but my 81 has only one wire on the o2 sensor. Thanks for any help.

 

[Dave L.]

02 sensor

Richard - A 1981 Corvette uses a 2 wire sensor. I checked my GM shop manual for a test procedure,it doesn't mention one. My guess would be if your not getting a trouble code or lean/rich condition leave it alone. When I installed my dual exhaust system 2 years ago I replaced mine for the heck of it.

Dave

 

[Richard Cooper]

Thanks Dave, the reason I asked this question is because I am getting a code 23. It is open or grounded M/C solenoid.

 

[KOPBET]

Do you have a high impedance DIGITAL volt meter? If so you can check O2 output. Rich mixture = low oxygen = >900mv. Lean mixture = high oxygen = <200mv. Run engine at 2000 RPM for several minutes. Artificially enrich mixture by partially closing choke or adding propane. Artificially lean mixture by creating a vacuum leak.

 

[KOPBET]

Richard, it seems you have been working this problem for a long time. Have you given up on previous threads you started in November? Were you able to try Rare81's suggestions?

An O2 sensor with no output could cause the m/c solenoid to continually try to drive to a rich mixture setting. Check grounding of it also perhaps.

 

[Richard Cooper]

Kopbet, yes, this has been driving me crazy for a long time now. If I remove the plug from the M/C valve and apply power from the battery the valve will click everytime I touch ground. Also, there are no brakes in the wires from the valve to the computer. I cannot get the valve to click when I turn on the key to accessories and have the test pulg jumped out. Everyone tells me the solenoid should click when I do this, but it does not.
I have replaced the computer and O2 sensor, but still no click.
Thanks for your time.

 

[KOPBET]

questions:

1. On the two wires to the solenoid, one should be at battery voltage and the other could be either floating or grounded. Check resistance to battery ground with DVM.

2. Have you verified the output from the O2 sensor and the TPS ?

3. Have you checked the dwell ?

4. Does the PCM have a good ground and +B.

Check with engine warmed up.

 

[Richard Cooper]

Kopbet,
Yes, the plug to the M/C has battery voltage and a ground.
No, I did not check the output of O2 and TPS, because I'm not sure how to do this.
What is PMC and + B ?
Thanks for all your help, I know I should really take the car to be fixed, but as I stated in earlier post I have just lost my job. After 15 years my plant has decided to move to Fuchon, China. I am 58 years old and am having a hard time finding work. There is not very much work where we live, in upstate New York. I am working till July 25th. But, I have a good package from work, they are giving us a weeks pay for every year we worked plus I have vacation time saved so I'll get 20 weeks pay. I can take it one week at a time and still have all my benifits so its not to bad.
Thanks again for all your help, I am going tomorrow to buy a dwell meter.

 

[KOPBET]

If you have a ground on that lead (i.e zero ohms resistance to ground measured with ohmmeter ) all of the time then I believe that is exactly what the code 23 is telling you and this is not the way it should be, with the engine running and warmed up. This being the case I would suspect something is telling the computer to enrich the fuel mixture since you indicated that you had already replace the computer. Two things I believe will cause this would be NO input or < 200 mv from the O2 sensor indicating a very lean condition, or the throttle position sensor indicating greater that 80% throttle or WOT. You should be able to find test procedures on the Web somplace or post a thread. I believe this sensor is just a three wire resistance sensor with gound on one end and + voltage on the other with a lead attached to an internal wiper to vary output with movement. Check with a meter.
I don't know what carb you have but it should be easy to find.

I should not have said PCM, powertrain control module, and should have just said ECM or just computer. The +B is another term for positive battery voltage.

If the one lead is grounded all of the time I don't think you will have a dwell anyway since the solenoid is continually on, so maybe you could hold off on the purchase if you need to save cash.

 

[Richard Cooper]

Kopbet,
Again, I thank you very much. I will go out over the weekend and check out all the things you mentioned.
Its VERY nice of you to take all this time to help me with my problem. I have replaced all my body mounts in my vette so if you ever need any help with this just let me know.
Take care and enjoy the long weekend.