Oxygen Sensor Nightmare

[Sixdux]

The check engine light came on, ran the OBDII scanner and P0141 code came up. Which was Bank 1, Sensor 2. Went down to the local auto parts store picked up a Bosch sensor. Replaced sensor cleared code and light came back on after being driven 25 plus miles. Checked code again same code appeared. Went and replaced sensor that was purchased earlier just in case it was bad and the newer sensor produced same code. Any suggestions on what could keep producing this code?

 

[rockola1971]

Could be bad wiring harness to O2 sensor(heater wires). Bank 1 Sensor 2 is drivers side after the Cat(AKA Post cat).
Post Cat O2 Sensors only purpose is to monitor the 02 level coming from the cats and that value is compared to the Pre Cat sensors. The Post should be substantially lower than the Pre's if the Cats are doing their job. A common misconception about Post cat sensors is that they provide the PCM information for fuel injection control (Air to fuel mixture) and that is not true. Only the Pre Cat O2 sensors provide that information.

P0141 is a Bank 1 Sensor 2 Heater circuit malfunction. The O2 sensor has mini heating elements inside them to get them hot quick so the vehicle can go into closed loop faster. An O2 sensor doesnt provide valid signals (Data) until they are very hot and up to temp.

Watch Eric of the South Main Auto diagnose the problem.

You are probably going to need a voltmeter/ohmeter unless you find an obvious problem visually at the harness. The odds that both new sensors had bad internal heating elements are low so id look real good at the harness.

 

[afpj]

Check your O2 sensor fuses under the hood. If you didn't unplug the battery before changing the sensor, you may have popped the fuse to the heater circuit. I only needed to do that once and waste an hour chasing it down. I got codes for both sides though as I did both postCATS at the same time, as should you (always change in pairs). I didn't see the video it may have covered this.

 

[rockola1971]

Check your O2 sensor fuses under the hood. If you didn't unplug the battery before changing the sensor, you may have popped the fuse to the heater circuit. I only needed to do that once and waste an hour chasing it down. I got codes for both sides though as I did both postCATS at the same time, as should you (always change in pairs). I didn't see the video it may have covered this.

He had the heater circuit code (P0141) BEFORE he ever changed a O2 sensor. So if he does have a fuse blown, it isnt because he blew it. It blew for a reason... Short to ground from the heater 12v feed in that O2 sensor harness or internal short to ground in the sensors heater element.

You WILL NOT pop a fuse unplugging an O2 sensor... Unless you touch the receded positive pin in the O2 plug to ground. Is that even possible? 99% of the time a fuse pops because the current flowing through it exceeds its rating. So its doing what it is suppose to do. The other 1% is a fuse that has become weakened (its fusible element) form hot/cold cycling and/or vibration and just mechanically breaks in half. (AKA a stale fuse which is really an incorrect term/reason).

 

[Yukon2000xl]

Sounds like it could also be your cats are due


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[afpj]

He had the heater circuit code (P0141) BEFORE he ever changed a O2 sensor. So if he does have a fuse blown, it isnt because he blew it. It blew for a reason... Short to ground from the heater 12v feed in that O2 sensor harness or internal short to ground in the sensors heater element.

You WILL NOT pop a fuse unplugging an O2 sensor... Unless you touch the receded positive pin in the O2 plug to ground. Is that even possible? 99% of the time a fuse pops because the current flowing through it exceeds its rating. So its doing what it is suppose to do. The other 1% is a fuse that has become weakened (its fusible element) form hot/cold cycling and/or vibration and just mechanically breaks in half. (AKA a stale fuse which is really an incorrect term/reason).

oops, can't delete...See next post...

 

[afpj]

Duh, didn't read op post carefully enough. BTW, I cannot remember what brand I ordered from Rock Auto a few yrs ago (think it was denso) but the sensor plug was wired incorrectly from the factory. That's what popped my fuses most likely. Rock Auto rep noted I was not the only one. They let me keep the part since it was useless and when I pulled the old sensors & took apart the plug, it was like the 4 wires were all rotated by one on the new ones. Weird. I figured unplugging the battery would be a good idea for the future, but I thank you for the clarification.

As for OP, updates?

 

[rockola1971]

Sounds like it could also be your cats are due


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Throwing the heater circuit code would NOT mean the cat is bad.