Code P0133 - replaced O2 sensors but CEL returns

[ebbjak]

So I pulled code P0133, nothing else. Based upon what I read, I replaced both pre cat O2 sensors and cleared the codes. About 30 miles later the CEL came back on. Again it was indicating P0133. I checked connections and reset the codes. Again, about 30 miles later the CEL came back on. Thoughts?

[JFP in PA]

Originally Posted by ebbjak

So I pulled code P0133, nothing else. Based upon what I read, I replaced both pre cat O2 sensors and cleared the codes. About 30 miles later the CEL came back on. Again it was indicating P0133. I checked connections and reset the codes. Again, about 30 miles later the CEL came back on. Thoughts?

Year and model of the car would be helpful.

You may now need to hook the car up to a Porsche specific scan tool like the Durametric system so that you can see the O2 sensor voltages in real time in order to find out what is going on.

[ebbjak]

whoops. sorry. 2001 Boxster S 38,000 miles. I have a new scan tool scheduled to arrive tomorrow that I can use to check further

[ebbjak]

[bell]

What is the fuel trim (adaption) reading? Could easily be vacuum leak related

[matt demaria]

According to Poses, P0133 is Signal period for bank 1 is ageing. "With an old senso, the duration of the period is too long..." The period is measured at .2V on the rise ramp to .1V on the falling ramp. The limit is about 1 second for an old sensor.
Your software has indicated an issue with B2S1. Is your software accurate or is Porsche's software off? I have seen issues with Porsche's software misidentifying the engine banks. But there is an issue with B2S1. You also might have a problem with the new sensor you installed. You can unplug the sensor to verify whether it is bank 1 or 2.
IIRC there might have been a TSB for reflashing the DME for an O2 issue for your car.

[roofrack]

If you don't mind me asking, what kind of scan tool did you get?

[yupaleus]

I had a persistent cel for 7 yrs. off and on. Changing the regurgitation tank vent line/valve seems to have cured it for me...about 200 mi cel free, a record, knock on wood

[ebbjak]

The fuel trim is unremarkable. The Long Term fuel trim is constant at .73 and the short term most common reading is .76 but varies with the highest going to 5.7 and then almost immediately going to -5.7.

[ebbjak]

It is an OBDII Bluetooth adapter made by BAFX Products, you'll also need Torque Pro app for or something similar for your smartphone to plot the data above.