o2 sensor issue

[dorianhellas]

Been getting CEL from o2 sensor after replacing oil and changing MAF sensor. I replaced y pipe cats and replaced all 4 sensors. All sensors test good however bank 1 sensor 2(which is what CEL is for) runs at super low volts on and off. Next thing I am doing is replacing the computer...anyone have this issue or know of any solutions to this?

 

2003 GMC Sierra 1500 2WD, 65k miles

[txab]

I'd thoroughly check the wiring

[dorianhellas]

from the one sensor to the computer? or for the computer?

[rjgti]

from sensor to ecm

[Bad Bowtie2]

Stay with AC Delco parts too!!

[Supreme Pizza]

If I understand you correctly, your getting an O2 sensor code after working on the car and replacing parts.

 

I would check to see if any of the other 02 sensor have the same part number. If so, switch them. If the code follows the sensor, guess what the problem is...

 

If the part numbers don't match, try buying another 02 sensor and install it. Sometimes sensors are bad from the factory. Buy a handful of them from a self service junk yard and test each one to see if it will make the code go away.

 

If the issue is confirmed to be NOT a sensor issue, then follow the problem upstream. The most likely places to find the problem, is where ever you were working with tools. Obviously there could be an exhaust leak on that "Y" pipe that you changed. Or maybe the "MAF sensor" got messed up when you were fiddling with it.

 

My money is on a bad sensor or an air leak in the exhaust.

 

Test for exhaust leaks by starting the engine, and then stuff a rag into the exhaust pipe. Then feel around all the exhaust connections (without actually touching the HOT exhaust pipe) for puffs of air coming out of a gasket or doughnut.

 

Once the problem is solved, the code wont magically disappear that second. A code can take a very long time to clear itself after the problem goes away. Each time you think you may have fixed the problem, clear the codes and see if it comes back. You can buy an OBD2 code reader on eBay for about $15, or a really fancy one for $30. You can also clear the codes by disconnecting the battery and then turning the ignition or headlights on. Most auto parts stores will clear the codes for free as well. Speaking of codes, you would be surprised how many times codes will simply go away and not come back after clearing them, even if no repairs were performed.

 

Note: The O2 sensor generates it own electricity, based on how much oxygen is in the exhaust. So if the sensor is not sending the anticipated voltage to the computer, then either the sensor is defective, or the sensor is working correctly and the exhaust gases that it is coming in contact with are of the incorrect mixture. Example: drill holes in the exhaust pipe upstream of the left O2 sensor, and smash the right O2 sensor with a hammer. The codes from the left and right side may be the same, depending on the configuration of the emissions system.

 

Upstream sensors fine tune the fuel mixture. Downstream sensors monitor the performance of the catalytic converter.

 

 

Anywho.... That's probably more than you ever wanted to know about O2 sensors.....