O2 Sensors CEL

[SNaray8442]

I've got a CEL for my o2 sensors. The OBDII tools at AutoZone picked up a P1144 and P1146 which shows up as o2 ground fault, the porsche tool at the dealership pulled 2 O2 sensor codes, I think 037 or 039, I wish I would have written it down.

Anyway, if I delete the codes/reboot the ECM it takes about 100 miles to come back.

It seems like it always pops up when I'm getting on it at high speeds.

Any ideas how I should troubleshoot this?

Thanks!

[Loren]

Model and year of your car please....

[SNaray8442]

It's a '99 C2, sorry.

VW specs say "long term fuel trim adjustment - bank 1/2 too lean"

[Izzy]

I would start with cleaning the MAF. Do a search and you will find a good bit of information on cleaning MAF. That doesn't do it, you may need new O2 sensors, which are easy to do if you have to. Close to or over 60K miles?

[SNaray8442]

69k miles.

I just pulled one of my o2 sensors and it looks like it's been running pretty lean. The tip's pretty white/orange looking.

I'll clean the MAF and see what happens, thanks.

[Loren]

Perhaps you mean P1124 and P1126?

P1124 Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Rich Threshold

P1126 Oxygen Sensing Adaptation Area 1 (Cylinders 4 . 6) - Rich Threshold

These codes mean your car is running too lean - and the DME can not correct for by making the mixture richer.

This is usually caused by an air leak or an incorrect air flow reading.

So check for leaks and try cleaning the MAF as Izzy suggested.

[SNaray8442]

Yes, 1124/6. Thanks Loren.

I pulled the airbox out, cleaned the MAF and the O2's.

There also seemed to be a small leak at the filter on the back right of the airbox.

It's all back together now and the car feels like it's gained some pep. Maybe it's just in my head, though.

Thanks!

[Izzy]

The reason I was asking about the mileage was for the O2 sensors. Not out of the ordinary to need replacing past 60K. They run about $120 if cleaning doesn't do the trick.

[1schoir]

Yes, 1124/6. Thanks Loren.

I pulled the airbox out, cleaned the MAF and the O2's.

There also seemed to be a small leak at the filter on the back right of the airbox.

It's all back together now and the car feels like it's gained some pep. Maybe it's just in my head, though.

Thanks!

SNaray:

If you have to get the 02 sensors, don't spend the extra money for the "Porsche" part with the Porsche Part number. Get the equivalent Bosch part. Same part, but no Porsche box or part number stamped on it. Porsche does not manufacture 02 sensors, Bosch does. The Bosch part is exactly the same, and has the correct connector.

Regards, Maurice.

[slbates]

Yes, 1124/6. Thanks Loren.

I pulled the airbox out, cleaned the MAF and the O2's.

There also seemed to be a small leak at the filter on the back right of the airbox.

It's all back together now and the car feels like it's gained some pep. Maybe it's just in my head, though.

Thanks!

SNaray:

If you have to get the 02 sensors, don't spend the extra money for the "Porsche" part with the Porsche Part number. Get the equivalent Bosch part. Same part, but no Porsche box or part number stamped on it. Porsche does not manufacture 02 sensors, Bosch does. The Bosch part is exactly the same, and has the correct connector.

Regards, Maurice.

Maurice, good point. I found the Bosch part number to be significantly cheaper. I will have to look, but I think I found them for around $110 +/- last year.

For a 99 996 C2 I purchased the following:

Bosch #13564 ( before cat)

Bosch #13723 (after cat)

Maurice is correct that the box does not have a Porsche part number anywhere but the sensor itself is stamped with several different numbers including the Porsche part number. For example, Bosch #13723 has the following numbers stamped/engraved on the sensor ( as best I could read them at the time) :

LSH 25

993.606.118.01

0 258 003 723

5812833 12v 982

Lastly, the Bosch part number sensors I purchased were made in the USA in lieu of Germany. Both sensors were plug and play and came withe the correct connectors to plug directly into the harness.

[SNaray8442]

I only cleaned one, and the code came back today. I've got to run back and have it scanned to see if it's just one or both.

[SNaray8442]

Cleaned O2 sensors and MAF liberally with "MAF Cleaner". Code came back.

MAF looked pretty much new, O2 sensors looked kind of white. Definitely running more lean than rich.

What should my next course of action be?