DIY for O2 sensor replacement

[texomawaves]

Please help me find a good DIY for O2 sensor replacement. I read the code on my Durametric indicating a OS sensor is out. Thanks

[crumbum]

Have you seen the technical articles on the Pelican Parts site?

Pelican Technical Article: Boxster Oxygen Sensor Replacement - 986 / 987

[Topless]

What codes did you get? The code will indicate which O2 sensor is the problem.

[texomawaves]

I got a P1126. I also got a P1124 (fuel pump relay final stage). These two always come in at the very same time. I figured I'd know it if I had a fuel pump issue. I've replaced O2 sensors in the past, so I figured I'd attack that issue first, then see if the CEL comes back. Thanks! Chris

[JFP in PA]

Originally Posted by texomawaves

I got a P1126. I also got a P1124 (fuel pump relay final stage). These two always come in at the very same time. I figured I'd know it if I had a fuel pump issue. I've replaced O2 sensors in the past, so I figured I'd attack that issue first, then see if the CEL comes back. Thanks! Chris

Sorry, but neither of those codes are necessarily fuel pump relay related. Both codes indicate that O2 sensors on both cylinder banks are running so lean that the DME cannot make up for it. Most often when you see this, it is not a fuel delivery issue, but a vacuum leak in the intake system.

[Topless]

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.

[Topless]

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.

[san rensho]

Also, check the voltage and resistance of the O2 sensors with the Duramtric. If the values are consistent, then its unlikely its the sensor. You can also check for a vaccumm leak by looking at the MAF, ignition angle, RPM and all FRA/RKAT values. If the MAF is low, say below 12 and the RKAT is +3 or 4, (should be 0) its a good indication you have a vacuum leak.

[texomawaves]

You guys are so helpful, Thank you! I'll check all this out tonight and report back. :dance:

[texomawaves]

I played with my Durametric (enthusiest version) and it is indicating Motronic 5.2.2. I'll attach some interesting photos. I'm thinking I might have a bug in the Durametric application itself. BTW, I couldn't find the other parameters like MAF and RKAT. Sorry my photos are sideways (darn iphone).

[Topless]

Wow! If your Durametric software gives you bogus information about your fault codes it is surely goofed up or not very useful at best. Here is the description from Porsche.

Scroll down for relevant codes:
http://www.pelicanparts.com/techarticles/Boxster_Tech/19-FUEL-02_Sensor/OBD-II-scan.pdf

[texomawaves]

I haven't thrown a code since I reseated my oil filler cap. That has been almost a month of driving since, so I think that might have been the problem!!! Maybe the o-ring on the filler cap is wearing out.

[mikesz]

how long after you fix the problem will the cel light go off? or do you have to reset it?