DIY for O2 sensor replacement

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Your O2 sensors are probably fine.

From Loren over on Renntech:
"P1124 - Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Rich Threshold
P1126 - Oxygen Sensing Adaptation Area 1 (Cylinders 4 - 6) - Rich Threshold
The ODB II manual says that these codes indicate your fuel mixture is too lean. That is, the DME can not make the mixture rich enough - i.e. rich theshold exceeded.

It lists as probable cause:
Intake air system leaking.
Fuel pressure too low.
Fuel pump volume too low.
Fouled fuel injectors.

There is a TSB 4/00 03.. Oil Filler Cap (dated 3-24-2000) that states: "If the oil filler cap is not fully engaged, or is tilted, (not engaged on both sides) the filler cap o-ring will not provide a complete seal. This can cause a CE light and Pcodes: P1124, P1126, P1127, P1128." This would be my first try.

If that is not it. You can likely rule out the last one (since you got codes for both sides) - as a having a fouled fuel injector on each side of the engine is very unlikely.
I would look for loose or worn vacuum hoses or other manifold leaks. You might also replace your fuel filter if you have not replaced it in the last 30,000 miles. "

An intake air leak could be a bad oil fill cap, bad AOS, bad gas cap, failed vacuum tubing, cracked oil filler tube, torn rubber intake etc. These are your most likely fixes. A process of elimination will find it. A bad fuel pump or fuel filter is possible but less likely.

+1 on avoiding combustible leak detectors: propane, carb cleaner, brake cleaner etc. Engine flash fires are fun but no fires are better. Been there done that<8^)

[texomawaves]

All great information!!! Thank you very much. I'll start with the simple basics tonight. I'll be changing out brakes so I'll have my hands dirty I'll report back any findings. Thanks again! :dance:

[texomawaves]

I find it strange why my Durametric said P1126 was a fuel pump relay. I'll have to see if I need to upgrade my app. I hope so! I paid $300 for it.

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Originally Posted by texomawaves

I find it strange why my Durametric said P1126 was a fuel pump relay. I'll have to see if I need to upgrade my app. I hope so! I paid $300 for it.

Maybe just a setup issue with your software. Different error codes mean different things depending on your car's DME. a 98 Boxster runs Motronic 5.2.2, a 2003 Boxster runs Motronic 7.8 with different error codes for each.

Make sure your Durametric software knows you are plugging into a Motronic 5.2.2 car and it will probably get it right.