CEL P1128+P1130 HO2 Sensors cause?

[rollafson]

Hi,

My first post (and I did search before posting) - couldn't find anything specific to indicate the cause of a CEL with the following diagnostic codes:

P1128 Upstream Heated O2 Sensors Swapped

P1130 Lack of HO2S Switch – Adaptive Fuel at Limit

Cleared CEL and sure enough after a few days it came back. When starting, it's taking noticably longer for the engine to catch. Not sure I should be driving this now for fear of doing damage to the cat or something...

Can anyone advise a course of attack to identify and then fix this problem? Other posts indicate the air system, such as bellows etc, but some more precise pointers would be invaluable.

Car is a UK 996 C4 / 2001. Has had big service three months back (filters, fluids, plugs etc).

Many thanks in advance.

DJR.

[Loren]

P1128 Oxygen Sensing Adaptation, Idle Range, Bank 1 – Above Limit

P1130 Oxygen Sensing Adaptation, Idle Range, Bank 2 – Above Limit

Potential causes:

– Incorrect signal from MAF sensor

– Intake air system leaking

– Fuel pressure too low

– Volume supply of fuel pump too low

– Fuel injectors fouled

– Exhaust system leaking

[rollafson]

P1128 Oxygen Sensing Adaptation, Idle Range, Bank 1 – Above Limit

P1130 Oxygen Sensing Adaptation, Idle Range, Bank 2 – Above Limit

Potential causes:

– Incorrect signal from MAF sensor

– Intake air system leaking

– Fuel pressure too low

– Volume supply of fuel pump too low

– Fuel injectors fouled

– Exhaust system leaking

Thanks Loren - amazing response. I'll start looking for leaks in the intake and exhausts, as I'm thinking they'll be the easiest to spot first. Then I guess the fuel pump is the next easiest. Injectors I'll address last. But what about the MAF sensor - it seems these are problematic generally? Any quick and easy test to elimate the MAF sensor, as it's a costly component to replace?

Again, sincere thanks.

[Loren]

If your mid-high RPM performance is poor then it is likely the MAF.

Either way I would start by cleaning the the MAF (as documented here elsewhere).

[Palma308]

Hi,

My first post (and I did search before posting) - couldn't find anything specific to indicate the cause of a CEL with the following diagnostic codes:

P1128 Upstream Heated O2 Sensors Swapped

P1130 Lack of HO2S Switch – Adaptive Fuel at Limit

Cleared CEL and sure enough after a few days it came back. When starting, it's taking noticably longer for the engine to catch. Not sure I should be driving this now for fear of doing damage to the cat or something...

Can anyone advise a course of attack to identify and then fix this problem? Other posts indicate the air system, such as bellows etc, but some more precise pointers would be invaluable.

Car is a UK 996 C4 / 2001. Has had big service three months back (filters, fluids, plugs etc).

Many thanks in advance.

DJR.

[Palma308]

DJR

Did you ever discover what the cause of the CEL . The reason I ask is that I to have the same problem on a 2001 996 C2 with only 16k miles on it.

Thanks in advance

Vaya Con Dios

Palma308

[rollafson]

Hi,

I did make an attempt but the limited engine access makes for finding air leaks rather difficult! I'm pretty sure that's what it is, as covering the air intake to the engine doesn't yield the change in engine note that I'd expect, and otherwise the car isn't missing. I know an excellent chap with a smoke machine, so that's what I shall try late this week. If you can wait a few days, then I'll update you. I'm expecting a vacuum hose to have perished somewhere with our freezing UK weather...

br/David.

[rollafson]

Problem found (by someone more competent than me!) to be a split bellows hose - probably due to the cold weather and the fact that the car is 7 years old. Hope this helps. br