Contour Enthusiasts Group Archives Forums General Troubleshooting o2 sensor troubles

Quick rundown:
- Got code p1131 (bank1 upstream O2 sensor)
- Bought two OEM motorcraft sensors and had a mechanic
replace bank1 & bank2 upstream sensors.
- Codes are gone.
- Few day later got code p0161 (bank2 downstream O2 heater circuit)

Basically the new code is coming from a sensor that shouldn't have been touched at all, so I'm getting ready to check out that O2 sensor & wiring visually, but before that I'd like to get some more information from you guys...
It is possible, but probably unlikely that the appearance of the 2 codes are unrelated. More likely something happened while replacing the O2 sensors, maybe he installed the sensor(s) in the wrong place...
Is it possible to install the upstream sensor in the downstream socket? (if so will it work properly or can it be the cause for the new code?)
Any other ideas what could have happened? (other than maybe him knocking off the harness or something)

Thanks,
Krisztian

"Few day later got code p0161 (bank2 downstream O2 heater circuit)"
If you ran over a puddle of water, and the water got on the connector, you could get this code. I got one for a Bank 1 lower a few months ago driving in the pouring rain.

" maybe he installed the sensor(s) in the wrong place..."
This is easy to check for the Bank 2 O2 sensors. Look under the radiator. If the lower sensor (driver side) looks new compared to the upper one (passenger side and nearest to the oil filter), then you know he installed the wrong sensor for you.
On this 2-D picture, ignore the red box and arrow, the Bank 2 Upper is the sensor on the left of the pre-cat in this picture (passenger side). The arrow is pointing to the Bank 2 pre-cat. The Bank 2 lower is the one on the right in this picture (driver side)

Originally posted by chongo:

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