I have a 90' cavalier and I was getting an O2 code from the computer. I replaced the sensor about 1 month ago and all was fine. Now the light is back on again, flashing the same code 13 & 44. How do I test the sensor to see if it is working or not?

Thanks!

 

On my 86' cavalier... you could always tell when it needed an O2 sensor as the idle was way too fast.

 

Properly testing a oxygen (O2) sensor is complicated but I'll tell you how to do a quick test to see if it is dead or almost dead. This is a single wire o2 if I remember correctly.

You'll need a good digital volt/ohm meter and a jumperwire. You will have to make up the jumper wire so it will attach between the o2 sensor connector and the harness connector. Also, strip some insulation off the jumper so you can attach you test lead to it.

Ok,
With the engine cold, unplug the the o2 sensor connector and install the jumperwire between the male and female ends. Attach the positive test lead of your meter to the jumper. Attach the negative test lead to ground or the negative side of the battery. Set your meter to Volts DC, you'll be testing in the 0-1 volt range so select MV range if you can.

Now start the car and let it warm up for a few minutes, then fast idle it at 2000 rpm for 2 minutes. The o2 should be working at this point.

Now look at the voltage. It should be fluctuating from around 200mv to about 800mv. If it is fixed high (above 500mv) pull a vacuum hose off the intake to create a vacuum leak. This should make it go very low to around 100mv.

If it is fixed low try blipping the throttle to see if it goes high 700mv or higher.

If you can't get it to move then it's bad. If it does move it can still be bad but you need a Labscope and some training to diagnose it further.

Hope this helps and don't burn yourself on the exhaust...

 

Thanks!