# Just a faulty O2 sensor? (P0138)



## teoball (Nov 12, 2012)

I had a problem with high oil consumption (I thought) on my Nissan X-trail 2003 2.0 petrol (T30). I took a complete service at my local Nissan dealer with oil/oil filter change, but after approx 7500 km on the road the oil level was below the dipstick and the timing chain didn't get enough lubrication (rattling sound). Re-filled with 2 liters of oil and good to go. 

I asked my dealer if this was normal and they adviced me into having the car for an inspection. A few days later I was told that the catalyst in the catalytic converter was getting damaged and breaking away and also that fragments of catalyst had entered my engine damaging the cylinders and piston rings, hence the high oil consumption. They wanted to change the catalytic converter and the piston rings and also hone the cylinders. The price was awful high ($ 8000) and I found out that I could just buy a new catalytic converter (98306 Catalyst Converter NISSAN PRIMERA, X-TRAIL - Skruvat.com Car parts & accessories Online) and have a cheaper to install it for me. They did and didn't find any worn piston rings and no problems with the cylinders. They also changed the engine oil and oil filter. 

The second day after the repair I got this yellow alarm lamp in my dashboard. After googling some car forum posts I found the error code to be P0138 -> O2 Oxygen Sensor Circuit High Voltage (Bank1, Sensor2) after using the "trick" with the gas pedal (http://www.nissanforums.com/l31-2002-2006/7500-all-you-ever-wanted-know-about.html ). The mechanic from the garage told me that my new catalytic converter was smaller than the original one, but it fitted anyway. I reset the alarm, but today it came back flashing frantically depending on how much I stepped on the gas pedal. 

Could this just be a faulty O2 sensor? Where is this located, which one to buy, and is it easy to remove the old one and install a new one? Any precations I should be aware of? Anyway, I find it strange that this happended just after installing my new catalytic converter.


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## rogoman (Dec 16, 2004)

O2 sensor #2 is located just below the CAT. Before condemning the sensor, check the electrical harness connectors.


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