Fault codes

[924nutter]

I have posted before about the "check engine" warning and had a talk with the garage. He is perfecty happy for me to publish the fault codes, which are as follows;
P1126 ox sensor bank 1
p1133 ox sensor bank 2
p1101 charge air measurement.
Just to remind interested parties, the air mass sensor has been changed with a test unit, and after 70 miles the check engine light came back on.
Current thinking is an air leak, possibly in the breather pipe at the back, or the breather pipe stub on or around bank one that can be broken if the engine is removed without undoing the clamp. I mention this in case the engine was removed to facilitate the fitting of the Tubi exhaust

 

[Richard_Hamilton]

P1126 356 Oxygen Sensing Adaptation, Lower Load Range, Bank 1 - Below Limit Diagnosis conditions • Oxygen sensing system active • Time elapsed after engine start-up: 250 to 350 seconds (USA) • Time elapsed after engine start-up: 302 to 402 seconds (RoW) • Engine temperature greater than 60 °C Possible fault cause ♦ Incorrect signal from MAF sensor ♦ Fuel pressure too high ♦ Fuel injector leaking P1133 358 Oxygen Sensing Adaptation, Lower Load Range, Bank 2 - Below Limit Diagnosis conditions • Oxygen sensing system active • Time elapsed after engine start-up: 250 to 350 seconds (USA) • Time elapsed after engine start-up: 302 to 402 seconds (RoW) • Engine temperature greater than 60 °C Possible fault cause ♦ Incorrect signal from MAF sensor ♦ Fuel pressure too high ♦ Fuel injector leaking P1101 Input Variables, charge measurement - above limit Diagnosis conditions • Engine running Possible fault cause ♦ Heavily soiled throttle ♦ Throttle adjustment unit faulty ♦ Mass air flow sensor faulty The common fault cause is the MAF, so I would try a new one.

 

[924nutter]

Thanks for coming back so quickly Richard. The indie keeps a test maf which has been installed in my 996 but to be honest the element in my original maf was quite clean and shiny. It is possible that a second unit has failed, but both the indie and I think this unlikely. Of interest are the comments about heavilly soild throttle or faulty throttle adjustment unit, because the engine does not always return to idle, preferring instead to sit at 1100 rpm quite frequently, so I think the evidence points to that. I am assuming that the throttle adjustment unit is a kind of servo device linked in to the emission system that maintains as close as possible the correct stoichiometric ratio when lifting off to prevent over lean and incomplete combustion. Many thanks I will pass this info on. Just to add insult to injury the brakes on my citroen ax gti runabout have developed a fault, so I am now down to the 944, although the 911 is running, and as posted in another thread, after three weeks it started like a dream today.

 

[Richard_Hamilton]

I'm not 100% sure, but I would imagine that the 'throttle adjustment unit' is the throttle body. The DME sorts out the air/fuel ratio from the engine sensors (MAF, lambda sensors, etc) to inject the correct amount of fuel at the correct time. You could try cleaning the throttle body, but all the symptoms point to the MAF. I would suggest using a diagnostic tester to measure the MAF readings at various engine speeds to see if they are consistent. Datalogging the values would be even better. If you want to borrow my Durametric tester you would be welcome, or I could hook it up to my PIWIS tester for you. What kind of tester does your indy use?

 

[924nutter]

Yes I hear you Richard, the trouble is my indie keeps a brand new MAF sensor for test purposes, which is used purely for diagnostic testing, by the process of substituting, then it is put back in its box. You seem to be suggesting that this MAF is faulty, as even with this fitted the fault returned after 70 miles. Re: tester I didnt see the complete process but it looked to me like he has a program installed on his laptop with which he interrogates or communicates with the cars system by connecting said laptop into the diagnostic socket. He may well have other equipment. He was greatful for the additional information and is going to check out the throttle body on Friday. I will take advantage of your offer to use your own test equipment if, ultimately, he can't get to the bottom of it. I think it best to see the process through with him before going elswhere. He didn't get his good rep for nothing. Meanwhile the 944 T cab has been providing adequate entetainment, and with a scant 44898 miles on the clock continues to astonish the local plebbery who think it is an ordinary 944 with the turbo badge looking so "stuck on afterwards" as it does.