I just got finished pulling the oxygen sensors off my car and both appeared to be fine. One had a dent in the outer part of the sensor and also there was a chunk of plastic gone on the connector. Anyway after checking them, i reinstalled them but left them unplugged. The car seemed to drive exactly the same. I'll know for sure tomorrow morning if its driving the same (i have a problem with it making popping noises when its cold). If it is driving the same as it did with the oxygen sensors, then wouldnt that mean the sensors are bad? Thats what i'm thinking but i dunno.
Oxygen sensor test, are they bad?
- Thread starter mr_tinkertrain
- Start date
351LX
Founding Member
You can check if they are bad by using a voltmeter that reads accurately below 1 volt.Oxygen sensors create their own voltage when they heat up.If you hook a voltmeter to it and drive around you should see it produce a voltage about 0.5-0.7 when you are cruising.It won't read accurately at idle because there isn't enough exhaust flow to get it hot enough.If it doesn't produce a voltage in that range replace it with a known good one and check the voltage it produces and compare.If you have more than one wire, the other ones should be there to heat it and you will have to figure out which wire goes to the actual sensor first.
Dump the codes and see what the computer says is wrong…
Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.
See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html
Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.
The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel.
The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.
When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.
Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.
Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.
The O2 sensor ground is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts
Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.
See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html
Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.
The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel.
The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.
When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.
Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.
Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.
The O2 sensor ground is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts
ECU5.0
Banned
how are those things you can buy from advanced auto that are code readers for the eec? i might pick one up because i dont think my check engine light works at all
you can use a test light if you dont have a CEL (as SD cars dont)....i have a reader from AZ - seems to work fine. i like the audible chirps cuz im normally trying to read the next step (while my typhoon fan is sucking the pages out of the book. LOL)... some wally marts sell them for 20 something bucks (not here though).
89MustangGX
I have nothing productive to add!
Your O2 sensors won't do anything while the car is cold -- they only work in closed loop mode. Just figured I'd throw that into the mix for something to think about when you're deciding if they're good or bad...
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