O2 Sensor Issues HELP!

[jcogley]

My 99 Q45 thru a PO140 noting that it faulted to an open circuit. I changed the sensor and light stayed out for approximately 1.5 week, (300 miles). The car just thru a P0138 "O2 Sensor Circuit High Voltage" at the same sensor. Anyone have an idea why this car is running rich? HELP?

[qsiguy]

Not necessarily running rich, could be a defective sensor.

[jcogley]

I ashould have noted that int was bank 1 sensor 2, (before cat). THe previous owner noted that he changed the first O2 less then 4 months ago. I'm wondering if I have a bad connector/harness. Anything else upstream that would cause the rich conditions. I know the O2 sensor tries to adjust lean/rich conditions. If I'm correct, high voltage notes a rich condition.

[maxnix]

Sensor is a trim sensor for OBD II. Even though it is not primary, it will affect mileage.

[lakeq45]

Search for a thread from me on this same issue. I went through two O2 sensors (the second one was under the parts warranty fortunately) before the dealer gave me a loaner for a while and really dug into things. They checked all the harnesses, re-tightened grounds, etc etc. They ended up replacing the ECM (covered by an 8/80 from Infiniti) and everything has been kosher ever since. I kept lossng the right bank number 2 if memory serves, but it should be in the old post. Might take advantage of that 8/80 if it still applies to you. I was luck, ended up with 3 O2 sensors (they killed another one while they had the car) and an ECM for the cost of one O2 sensor.

BTW. If you replace the ECM be sure to re-bless ALL of your keys. My Q got a ride back to the dealer on a flatbed on their dime because they forgot to remind me to bring in my wifes key. It was my first time with a brain transplant. Only takes once.

[lakeq45]

Found the thread...started by QBaller

zerothread?id=179667

Looking at the date, this was about a year and a half ago and probably about 15k miles and I have not had any more problems since then.

[jcogley]

thanks Lake..Great info