MAF replacement - reset codes?
 

Is it necessary to disconnect the battery and reset/clear the codes after replacing the MAF?

Drive cycles will reset as the ECU learns what is normal.

To clarify, I replaced the MAF several months ago in response to the car stalling at low idle. I installed a new Bosch MAF that I purchased on Amazon. The car still won't idle properly and stalls often at intersections. I also cleaned and inspected the throttle body, and replaced the idle control valve. I brought the car to my mechanic to read the codes and it showed a MAF failure code. Today I removed and cleaned the new MAF once more, but this time I disconnected the battery with the idea of clearing the codes and allowing the car to correct to the new MAF. It seemed to drive fine and never stalled. I'm cautiously optimistic though, and I'm not 100% sure I've addressed the problem. One thought I have is could the Bosch MAF I purchased on Amazon be defective? I've heard of this happening. Are the genuine Porsche MAF's so much more reliable? If the stalling resumes, I'll order a new Porsche MAF and see what happens. Any advice or comments?

Bosch makes the MAF for Porsche. Having said that, there are various MAF part numbers so make sure you used the .148 or .055 part numbers for an '01S.

Get the codes read, post them in the format Pnnnn here or use the forum's search function to see posts of prior owners who had the same code and see how they resolved. One nice thing about a car so old, someone else has discovered 99.99% of the problems already.

Don't throw more money at the problem until you know more.

Once you disconnect the battery, the air/fuel mixture is, for a few drive cycles, determined by preset default values and is not calculated from values sent by the MAF and O2 sensors.

Could the replacement part have been bad? Sure. Not likely.

Be sure to not touch any of the non plastic parts on the MAF.

More here.

Thank you for the wisdom. I checked the part number and it does have .055 on it (photos attached)
http://986forum.com/forums/uploads02/MAF11538517027.jpg
http://986forum.com/forums/uploads02/MAF21538517042.jpg
I purchased it from Amazon for around $151, but it sure is advertised as an OEM part. I'm assuming its fine. I had the codes read and it was a P0102 MAF. I disconnected the battery with the hopes of clearing the codes, and inspected the MAF one more time. It seems fine. Could it be the thing I purchased off Amazon is defective? I also heard that code could indicate a wiring issue such as a short, or possibly one or more of the oxygen sensors. I'm leary to just drop it off at my porsche mechanic with nothing more to go on. But the stalling problem is getting pretty frustrating. It seems to go away after the car is driven awhile and warms up, but for the first few minutes/miles, it stalls at every stop. Is there any sort of re-programming that needs to be performed by a tech when this part is replaced?

I heard that bad oxygen sensors could cause the car to stall. However, I haven't been getting a CEL, and the only code was P0102. Any more advice before I take the car to my mechanic?

Just replaced the new Amazon Bosch MAF with another new Bosch MAF, this time purchased from Pelican. Same exact part number. Car runs worse. Coughs, stalls, won't idle under 2500 rpm. Now I'm getting a CEL too for the first time. Running out of ideas. Sure could use some good advice!

So what is the code? And are there any others?

O2 wiring problems (short or disconnect) give off very specific codes. You really need to get the codes read and interpreted. Almost any problem you have has been had already by someone else and the resultant fix posted here so we can search. Some of us have factory manuals too.

Interesting update. So this time I disconnected both battery cables. Previously, I had only disconnected the negative. Codes and CEL were cleared. The car purrs like a kitten at idle, and drives fine. Took the car back to Autozone several days later to check codes again, and its clear. Live and learn.