OBDII Fault Code Question

[JFP in PA]

Originally Posted by mgfranz

I had a CEL come on yesterday during a simple freeway run. Since I do not have a DME but only a OBDII scanner I plugged it in. The errors were P1126 and P1133.

I know what the error codes translate to, what I am scratching my head with is why one code, (1126), would say "Oxygen Sensing Adaptation Area 1 (Cylinders 4 - 6) - Rich Threshold", and the other "Aging of Oxygen Sensor Ahead of Catalytic Converter (Cylinders 1 - 3) - Below Lower Limit"?

So does this mean that one side of my engine is running lean and the other rich? Or is it simply time to change them?

2001 2.7, 5 speed, 90,000 miles.

P1126 is an overly lean condition on cylinders 4-6 (air leak, low fuel pressure or volume); P0133 (note that is not the code you posted) is for an aging O2 sensor ahead of the TWC on the opposite bank (cylinders 1-3). And you do have a DME, but do not have the Durametric software, which I would recommend as "global" OBD II scanners often generate misleading codes on these cars.