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P1124, P1126 without usual suspects


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My ‘99 996 C2, 63K miles, totally stock, started throwing CELs a couple of weeks ago. The certification warranty expired end of June (planned obsolescence with precision German engineering!) :cursing: Initially got:

- P1124 (cyl 1-3 O2 sensor - Rich Threshold)

- P1126 (cyl 4-6 02 sensor- Rich Threshold)

- P0102 (Mass or Volume Circuit Low Input)

The P1124/1126 would re-appear reliably with a day’s commute. I got only two instances of the P0102 during a week.

So far tried:

1) Cleaned the MAF & MAF plug with circuit board cleaner

2) Checked for loose electrical connections at back of engine bay (looked like where O2 sensors plug in)

3) Checked (as best you can with this car) for loose/damaged vacuum lines, crack in oil filler tube, oil fill o-ring condition

4) Jacked it up and inspected (again, as best you can) the oil bellows – looked OK, no fresh oil at all in vicinity of the tube

5) Pried out the rear deck rug to see if any plugs to the DME were loose (didn’t look like anything had been touched there since the car left Germany)

6) Put in a new MAF – exact Bosch replacement for my non-e-gas C2

The new MAF had an impact: Idle seemed improved, as well as throttle response. Unfortunately, the CEL reappeared on my next commute. Got the P1124/1126 again, plus pending codes:

- P0130 (O2 Sensor Ahead of Cat (Cyl 1 - 3) - Intercore Short Circuit or Limited)

- P0150 (O2 Sensor Ahead of Cat (Cyl 4 - 6) - Intercore Short Circuit or Limited)

Porsche did the 60K servicing last month, so the car has new filters, etc…

Any ideas, folks? I’ve been getting my data with an Innova 3100 ODB II reader (paid for itself about 20 times over). Will the product sold at www.obd-2.com provide the additional O2 sensor readings, etc… to figure out what’s really wrong with this 996?

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As Loren told me recently, 60K is not too early to loose O2 sensor. There are two sensors per side. I got 60K and the MAF just got replaced.

I have the Autoengineuity OBD2 for Palm Pilot, and can read the O2 waveform. That would tell for sure which ones are out.

Last thing though, did you disconnect the battery while changing the MAF? If not, that is the last thing to try.

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The OBD2 Manual says:

P1124/P1126 - Fuel/air mixture is so lean that sensing has reached its rich threshold.

- Intake air system leaking

- Fuel pressure too low.

- Volume supply of fuel pump too low.

- Fuel injectors fouled.

P0130/P0150 - Oxygen Sensor Ahead of Catalytic Converter (Cylinders 1 . 3) - Intercore Short Circuit or Limited Voltage Increase

Fault conditions:

Crack in ceramic material

Reference air polluted

Short circuit in signal wire to sensor ground (intercore short circuit).

Fault area:

- Oxygen sensor

- Wiring harness

- DME control module

HTH

Edited by Richard Hamilton
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What is the vacuum reading at idle? Make sure the 4 bolts on the throttlebody are tight. What is your MAF reading at idle with A/C OFF? Make sure MAF is seated properly with good O ring and that entire intake is secure.

Throttlebody bolts are secure, as is all other fasteners and clamps on the intake/air cleaner body.

Where do you suggest I tap in to get a vacuum reading?

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What is the vacuum reading at idle? Make sure the 4 bolts on the throttlebody are tight. What is your MAF reading at idle with A/C OFF? Make sure MAF is seated properly with good O ring and that entire intake is secure.

Throttlebody bolts are secure, as is all other fasteners and clamps on the intake/air cleaner body.

Where do you suggest I tap in to get a vacuum reading?

Any vacuum line will work. What is your MAF readings at idle with AC off?

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OK, now I'm getting really perplexed. The CEL went off today, after 3 times the normal start/stop cycles of an average driving day (the relevant OBDII testing regime must be tied to engine starts). No, the CEL bulb isn't burnt out. I drive home, figuring my MAF replacement was the right diag :thumbup: and (as I read in a post somewhere) the "DME was getting used to the new MAF".

I get home and I throw my code reader on and I still have the same assortment of codes: P1124/1126 registered, P0130,0150,0102 pending! :eek:

Anyone ever see this kind of OBDII behavior before? Should I just short-circuit the whole process, and disconnect the battery as izzyandsue suggests?

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Yes, reset your codes and see if they come back.

120+ miles since I cleared the codes, no CEL, no pending codes :clapping:

A few observations:

While the various computers within the car were adapting to the replacement MAF, I experienced several periods of drivability problems: Idle hunting, flat spots in the RPM range, and other "non-linear feel" from the normally electric-motor-like boxer engine. At the time, I thought I'd dropped $270 on the part and I was still :censored:! Once it was all said and done, the car pulls like a freight train again...but it does take several days and multiple start cycles.

And several questions for the online faithfull:

1) Should standard protocol for a DIY'r be to disconnect the battery when replacing a MAF?

2) Is the answer to question 1 really dependent on how old everything is?

(eg, in my experience, doing this on a car with old plugs leads to several days' drivability issues).

3) What does Porsche do? Can they provoke reconfiguration to the new part with their equipment?

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  • Admin

A "re-learning" is needed whenever changing out the MAF and a few other critical DME controlled parts. This is normal and usually only takes a few miles and a short time. That is why Porsche techs test drive the car after a replacement. I think it takes a little longer if the car is a TIp as it has to re-learn it's mapping also.

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  • 2 weeks later...
My ‘99 996 C2, 63K miles, totally stock, started throwing CELs a couple of weeks ago. The certification warranty expired end of June (planned obsolescence with precision German engineering!) :cursing: Initially got:

- P1124 (cyl 1-3 O2 sensor - Rich Threshold)

- P1126 (cyl 4-6 02 sensor- Rich Threshold)

- P0102 (Mass or Volume Circuit Low Input)

The P1124/1126 would re-appear reliably with a day’s commute. I got only two instances of the P0102 during a week.

So far tried:

1) Cleaned the MAF & MAF plug with circuit board cleaner

2) Checked for loose electrical connections at back of engine bay (looked like where O2 sensors plug in)

3) Checked (as best you can with this car) for loose/damaged vacuum lines, crack in oil filler tube, oil fill o-ring condition

4) Jacked it up and inspected (again, as best you can) the oil bellows – looked OK, no fresh oil at all in vicinity of the tube

5) Pried out the rear deck rug to see if any plugs to the DME were loose (didn’t look like anything had been touched there since the car left Germany)

6) Put in a new MAF – exact Bosch replacement for my non-e-gas C2

The new MAF had an impact: Idle seemed improved, as well as throttle response. Unfortunately, the CEL reappeared on my next commute. Got the P1124/1126 again, plus pending codes:

- P0130 (O2 Sensor Ahead of Cat (Cyl 1 - 3) - Intercore Short Circuit or Limited)

- P0150 (O2 Sensor Ahead of Cat (Cyl 4 - 6) - Intercore Short Circuit or Limited)

Porsche did the 60K servicing last month, so the car has new filters, etc…

Any ideas, folks? I’ve been getting my data with an Innova 3100 ODB II reader (paid for itself about 20 times over). Will the product sold at www.obd-2.com provide the additional O2 sensor readings, etc… to figure out what’s really wrong with this 996?

I have a 996 / 99 C2 Tip car, I know first hand of P1124 P1126 codes as I was forced to drive with them for months before a dealer figured it out. Save your money there might be nothing wrong with your MAF. However there is a possibility you have two seperate issues. The real culprit of P1124 P1126 might likely a Crankcase Bellows tube located on the top rear of the motor. 996 107 237 52 Bellows tube, these go bad on all cars eventually and are very hard to get to with out a Lift to get the car at the right height and angle to replace it, a tear or hole in this tube will throw these codes.

My story.

http://www.renntech.org/forums/index.php?s...c=3583&st=0

If you search on "Bellows" you will find lots of info.

D Man

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My ‘99 996 C2, 63K miles, totally stock, started throwing CELs a couple of weeks ago. The certification warranty expired end of June (planned obsolescence with precision German engineering!) :cursing: Initially got:

- P1124 (cyl 1-3 O2 sensor - Rich Threshold)

- P1126 (cyl 4-6 02 sensor- Rich Threshold)

- P0102 (Mass or Volume Circuit Low Input)

The P1124/1126 would re-appear reliably with a day’s commute. I got only two instances of the P0102 during a week.

So far tried:

1) Cleaned the MAF & MAF plug with circuit board cleaner

2) Checked for loose electrical connections at back of engine bay (looked like where O2 sensors plug in)

3) Checked (as best you can with this car) for loose/damaged vacuum lines, crack in oil filler tube, oil fill o-ring condition

4) Jacked it up and inspected (again, as best you can) the oil bellows – looked OK, no fresh oil at all in vicinity of the tube

5) Pried out the rear deck rug to see if any plugs to the DME were loose (didn’t look like anything had been touched there since the car left Germany)

6) Put in a new MAF – exact Bosch replacement for my non-e-gas C2

The new MAF had an impact: Idle seemed improved, as well as throttle response. Unfortunately, the CEL reappeared on my next commute. Got the P1124/1126 again, plus pending codes:

- P0130 (O2 Sensor Ahead of Cat (Cyl 1 - 3) - Intercore Short Circuit or Limited)

- P0150 (O2 Sensor Ahead of Cat (Cyl 4 - 6) - Intercore Short Circuit or Limited)

Porsche did the 60K servicing last month, so the car has new filters, etc…

Any ideas, folks? I’ve been getting my data with an Innova 3100 ODB II reader (paid for itself about 20 times over). Will the product sold at www.obd-2.com provide the additional O2 sensor readings, etc… to figure out what’s really wrong with this 996?

I have a 996 / 99 C2 Tip car, I know first hand of P1124 P1126 codes as I was forced to drive with them for months before a dealer figured it out. Save your money there might be nothing wrong with your MAF. However there is a possibility you have two seperate issues. The real culprit of P1124 P1126 might likely a Crankcase Bellows tube located on the top rear of the motor. 996 107 237 52 Bellows tube, these go bad on all cars eventually and are very hard to get to with out a Lift to get the car at the right height and angle to replace it, a tear or hole in this tube will throw these codes.

My story.

http://www.renntech.org/forums/index.php?s...c=3583&st=0

If you search on "Bellows" you will find lots of info.

D Man

Thanks for the suggestion - I'd actually already read your post and done the contortionist act to inspect the bellows. In my case, it actually was the MAF.

What is the vacuum reading at idle? Make sure the 4 bolts on the throttlebody are tight. What is your MAF reading at idle with A/C OFF? Make sure MAF is seated properly with good O ring and that entire intake is secure.

Throttlebody bolts are secure, as is all other fasteners and clamps on the intake/air cleaner body.

Where do you suggest I tap in to get a vacuum reading?

Any vacuum line will work. What is your MAF readings at idle with AC off?

It's been a while (vaca, work insanity), and the car is running, but I wanted to close the loop. Per Car Code, I'm sucking a little over 5#/min at idle (AC off), and it goes up to 2.1+#/min when I rev it to 3 grand. This is natural induction - the car was stationary. I'm going to plug in the old, bad MAF and see what readings I get when I have the chance for the experiment.

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