error codes important or not ?

[rossa123]

Hi - I currently have two error codes on my 2001 Boxster and wanted to know in simple terms what they mean and is it necessary to have the car "fixed" - also if anyone knows what the "fix" procedure is.

the codes are P1128 Oxygen sensing adaptation area (cylinders 1-3)rich
P1130 Oxygen sensing adaptation area (cylinders 4-6)rich

Thanks for any help

[Richard Hamilton]

Those fault codes are mostly caused by a failing MAF sensor.

[Trev450]

As above, likely to be the Mass Air Flow sensor.

You need to get it into your local indy to get it hooked up to some diagnostic equipment to confirm and have the error faults cleared.

[NickUSA]

Richard Hamilton said:

Those fault codes are mostly caused by a failing MAF sensor.

Or likewise contaminated if running an oiled filter.

[thegoose]

NickUSA said:

Or likewise contaminated if running an oiled filter.

That's likely an internet myth - it's never happened in about 6 years of my 996 running a K&N, never had the MAF replaced in that time either. Fitted by Sports & Classic and serviced by them every year.

[Richard Hamilton]

thegoose said:

NickUSA said:

Or likewise contaminated if running an oiled filter.

That's likely an internet myth - it's never happened in about 6 years of my 996 running a K&N, never had the MAF replaced in that time either. Fitted by Sports & Classic and serviced by them every year.

It is over-oiling which causes the problem. S&C obviously know the right way to do it.

[Rockster]

Are there any other engine symptoms? How's the idle speed? Steady? Any stumble/hesitation moving from a stop? Are the oil level and coolant levels ok?

My 02 set the CEL and logged some error codes -- I do not recall what they were but they had me thinking "MAF" since they were related to air/fuel mixture issues -- and the problem turned out to be a bad AOS. (The first AOS failed at around 80K miles, the second around 100K miles later.)

Another time, prior to the above, something similar happened regarding the CEL and error codes and I ended up replacing the MAF. The error codes came back and it turned out to be a leaking oil filler tube cap. The MAF I replaced was just fine. I left the new MAF in service and after around 100K miles when it finally failed -- I forget the error codes/symptoms -- I replaced it with the original MAF that I had stashed in a box. The original MAF worked just fine and continues to work just fine.

For some adventurous owners they'll carefully disconnect the MAF from the electrical harness, use an OBD2 scan tool to clear any error codes. This among other things resets the fuel trims and other learned data to their defaults.

Then the owner just drives the car around normally. If the codes come back chances are it is not the MAF but something else. Be aware the CEL may come on with the MAF disconnected but the error code could be directly related to the MAF being disconnected. You have to read the codes -- do not erase/clear the codes though -- and verify from the codes the CEL is not on due to just the MAF being disconnected but the original error codes are back.

Be aware that if at any time the engine starts to act up in any way you should shut off the engine as soon as it is safe to do so and do not run it again. Let an experience/qualified tech do the diagnosing.

If after say a 30 mile drive if the CEL remains off or at least the same error codes do not show up carefully reconnect the MAF and clear the codes again and drive the car again to see if the codes come back. If they do... the odds are high it is the MAF.

If you want before you do the above let the warm to hot (operating hot) engine idle and with the rear trunk lid open check the oil filler tube cap to see if you can move it and if you can hear any air leak noise. If the cap is original I'd just replace it but that's me.

With the engine idling carefully unscrew the oil filler tube cap and remove it. If you have difficulty removing the cap -- I mean real difficulty -- this can be a sign the AOS is failing. However, without other engine symptoms even if the AOS is going bad it is probably not bad enough to subject the engine crankcase to enough low pressure to make it difficult to remove the cap.