OBDII Fault Code Question
 

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.

Thanks JFP, you are correct, that should have read Durametric not DME. And I did post the wrong readout for P1133, it should have been "Oxygen Sensing Adaptation, Lower Load Range, Bank 2 – Below Limit". But what could be the problem? I did recently, about 400 miles ago have to replace the fuel pump which failed, Bosch replacement...

I would suggest getting the car rescanned with a Porsche specific tool as a starter. If the overly lean code still shows, I would then check the fuel system for correct pressure and volume delivery. Have you changed the fuel filter on the car?

Yes, the fuel filter was changed at the same time as the pump. I will check the fuel pressure.

However what has not been changed in who knows how many miles is the air filter, and since I live on a ranch with lots of dust I'm sure it's way past it's life. I'm going to give the MAF a good cleaning and order a new air filter and see what happens.