code P1126

[da888]

Hey fella's. Been searching for any issues with only the P1126 code appearing which I understand could be alot of things.

 

I've cleared it multiple times in the last month and a half but it always comes back within a day or three. At different driving times and locations. Never anything similar. Engine is running great. Checked every where for a leaky vac. line, to gas cap, and oil cap, plus dipstick. Nothing.

Do I just buy a pre cat O2 sencor at this point or wait for more codes.

Thanks

2001 Boxster, 66k miles, all preventive maintenance done. Only the trottle body never cleaned yet.

[Loren]

You do not have a bad sensor - that sensor is telling you what the problem is.

 

P1126 356 Oxygen Sensing Adaptation, Lower Load Range, Bank 1 – Above Limit

 

Possible causes:

– Incorrect signal from MAF sensor

– Intake air system leaking

– Fuel pressure too low

– Volume supply of fuel pump too low

– Fuel injectors fouled

 

If you only have this fault not the bank 2 fault (P1133) then I would look for an air leak on bank 1.

[da888]

That's what I thought, but was getting frustrated cause I can't find anything. I've looked from the bottom while on the rack and looked from the top with the access cover off. Also tried new gas, and lucas fuel injection cleaner. Haven't checked fuel pump pressure though.

Thanks very much Loren and I'll report back if I do figure it out.

[flyingpenguin]

See if there are any exhaust leaks before the cats, ie. from the exhaust side of the motor, down the headers to the cats. Any air that seeps in would dilute the exhaust gas and could fool the O2 sensors into thinking the engine is running lean...

Edited August 5, 2015 by flyingpenguin

[da888]

See if there are any exhaust leaks before the cats, ie. from the exhaust side of the motor, down the headers to the cats. Any air that seeps in would dilute the exhaust gas and could fool the O2 sensors into thinking the engine is running lean...

Thanks for that advice, makes sense. We had it up on the lift recently twice looking for just what you mentioned, nothing. I've been running it for a week now with no code. But also added another Lucas fuels injector cleaner. Also have been adding Lucas's Ethanol treatment since I can't find anything less than 10% alcohol gas.

[da888]

Well a month has gone by and no more codes have come up. So I'll assume the injector cleaner has done it's job. So I'll close this discussion. Thanks all.

[da888]

Nope just came back on yesterday. But this time the P1133 is also with the P1126. So I'll research that and get back to you all.

Ok, cleaned the MAF sensor, but while checking vaccumm lines I noticed the vent hose from the power steering reservoir goes nowhere. Just hanging loose. Is there suppose to be a connection somewhere under trottle body housing ?

Well it seems it's just a vent and not connected to anything from my research. I think I'll rig up a smoke test next for the intake system. Try and fine leaks allowing air to come in. Or even using propane to see if idle increases.

Edited September 20, 2015 by da888

[da888]

Well put everything back together again after spraying the intake system with an alcohol based solvent I have, with the motor running. ( i've used this stuff as a starter fluid ) No uptake in RPM's anywhere. Cleared codes.

Sprayed the connector to the MAF sencor with an electrical cleaner that's suppose to enhance connections. ( 2-23) ( did not disconnect battery or MAF )

 

The next day I took it out for a ride and noticed it ran a little rough. Like when you disconnect the battery and the computer is relearning it's settings.

Started running better after a short trip. Later in the day on a much longer trip, I had to think this car is really running well. A little better than usual. So I guess I'll see if they come back and then do the pressure check. And find someone with an automotive smoke machine to look for leaks.

 

Well three weeks have gone by and all is good. No codes and idle is much smoother. So maybe the MAF sensor cleaning did the trick.

Edited October 9, 2015 by da888