CK911C4

Hello New member,
And new to me 01 911 C4 ,Purchased in Feb 15, 1 owner car , w/ 36 K mi. and now its at 45 k mi. Is it great condition. Black Metallic on Black. Mods done since purchase, H&R Lowering Springs, 4 Wheel alignment, K&N CAI., Wheels upgrade to 19" , rear fender wells trimmed for no tire rub, blacked out, Fab Speed Black chrome tips, RR Radio to Kenwood 6 in screej,

Recently had the alternator fail it was the stock one, Propeller not turning, 1st replacement was a Pep boys Life time China one, and it failed after 400 mi. I removed and replaced with exchange one at pep boys and the new one was a Bosh Refurbish, That looked much beefier than the china one, so as a FYI I think it depends on the core that gets returned or I had just got the wrong one from them in the beginning,
So installed the bosh and test voltage at battery and checked gauges and all seemed fine at just under 14 v. I would think twice before getting one from them. I was desperate because I wanted to race around all weekend,
So I took a chance.....

To relay all facts , my first attempt to take out the alternator I ran into a little problem and loosened up the throttle body and couplers that are attached to the motor. Only to get a little more room because I accidentally pulled off one of the small little hoses that travel under the throttle body to some were looks like possible vacuum hose for something not sure.
That being said I was able to get the small hose back on by moving the throttle body and got it all put back together. and all seemed fine and I drove the car about 400 mi. and alternator failed. the 1st one. CHINA "not recommended"
Now I swap out the alternator to the 2nd bosh refurbish out tagged from mexico one and I notice the coupler for the throttle body is shifted over and didn't look right to me. So I adjusted it so it had a better fit, this was hard for the back side kept wanting to get hung up but I did get it back together and tight. Started car all seemed fine.

Then went for a drive, and FYI I drive this car in the matter of what it was designed for racing and high rpm range, I'm always in the 4 to 6.5 K range when shifting and its a manual trans. Just the funniest way to enjoy these cars, I'm sure you can relate.

So once I'm in second or 3rd and do any RPM range above 5 k to 6 k , there is a change of power for a short sec. and then it comes back like its wants to just take off and haul ***... And during that transition the ABS & PCM light come on. Consistently and will go out on once car is turned off and restarted till I drive it at repeat the driving RPM as above.

Yesterday while testing it the CEL came on along with the other 2 ABS & PCM.
So frustration is setting in, But I remain calm. and get out my scanner and scan car and it returns P0102, and states "Mass or Volume Air Flow Circuit Low Input" . So I check a couple items that have been discussed about this issue.
1. Checked brakes and brake switch. All Good
2. Disconnected Neg side of battery to flash the ECU
3. Pulled MAF Sensor and blew it out. Made sure it was facing the filter. It was.
4. Checked all hoses and and intake for any visible signs of leaks
( Would like to know how to test for intake leaks that is more concise other then visual, ?
5. After complete reset of codes and removed neg wire off battery again I tested to see what readings I would get on a live data from the car on the MAF LBS/Min. when first started "cold" and running it had a voltage of 1.5 as car warmed up and dropped to normal idle it read 0.8 as I think it should. Parked and running the RPM s up data would change as RPM's changed. Is that any clue that the MAF is doing it's job ?

Also as another note I might have disconnected the MAF connector and tried to put in on backwards while the battery was still connected, could that have
blown the MAF sensor out and can I test the MAF sensor in some way to see if its OK or not. This might of happen on the 2nd alternator change out.

I just rechecked car on start up and ran RPM S up while parked and no lights come on, But it is not under a load either so I'm sure that had something to do with it.
Thank you in advance for anyone that could help me with this problem. Since these are the only cars I will own for sport from now until I die, I want to learn all I can on the DIY side with in reason and with in my means. I'm hunting for a turbo but I think I need a little more time with this one before I pull the trigger on Porsche dream #2 car. Kind Regards to all, CK

5CHN3LL

The lights are ABS and PSM, not PCM.

I believe the MAF connector is keyed - you'd have to whack it with a hammer to get it to snap closed with the connector reversed.

The MAF low voltage reading suggests that the MAF may need replacing. When you "blew it out," what did you use? The MAF is very delicate; it can be cleaned with electrical contact cleaner spray or MAF cleaner spray (the latter is sold at Autozone). The PSM/ABS warnings can be triggered by other things as well:

* Faulty brake pedal switch
* Aftermarket LED taillights

There are many threads, both here on Rennlist and on other sites as well, that explore the possible causes of this issue. Do some more Googling. For example, the first three hits returned if you google for the terms "996 maf brake light" - no quotes, just those four words - discuss several possible causes for your ABS/PSM light issue.

mharrison

MAF cleaner spray did the trick when I had similar symptoms.

CK911C4

5CHN3LL, Thank you for pointing out the PSM instead of PCM in my post , And I put it in the topic which is even worse. Forgive me.
I will take your advise and keep reading on. I have been on most of the common google sites and all forums prior to posting and some of the things to check are wide spread, so I was only trying to narrow it down a bit.

I don't have after market LED tail lights on the car yet, funny I just ordered some and there in my garage. I think there going to be going back after your heads up about a possible cause for trouble lights. Which is bring me to conclusion to be on the caution side before any further mods.
Thank you for your input

MHarrison, I will also be cleaning it with proper MAF cleaner today , will see what happens. Thank you

I also stopped by my mechanic who cares for my other cars which are British off road cars , and as soon as I told him I had an aftermarket CAI, both him and his mechanic said " take it off and put the stock one back on". And they stated CAI are OK for some off road cars put not good for sports cars like these. Especially MAF Cars. so passing that off which I'm sure has been written about as well. Thank you both and will be updating once problem is resolved and how. CK

CK911C4

Hers the follow up and what fixed it for me. and would like to thank MHarrison and 5CHN3LL for there input and help.
After mharrison advise I took my MAF apart and aftermarket intake and throttle body and cleaned the CAI with proper MAF Sensor cleaner & Intake Cleaner.
Put everything back together and went for a spin. I took it easy and the car was responding well. So I took it over 6K rpm in 2nd and no PSM off or ABS light on. I took it easy because I wanted to drive it over the weekend so I never went over 6K rpm in any gear and all was stable.

Later that week I went for a canyon run it was a Thursday just before Rennspot and I wanted to put it to the test.
Jumped on it a few times still not going over 6K rpm, then I hit 3rd and as soon as I went just over 6K rpm there they were bright as could be PSM off and ABS lights back on.

So now I 'm running with no MAF and I cut the run short and stopped by a local Porsche Indy shop and wanted to see what they had to say and if they could look at it and they could not till later next week.

But he said an interesting thing. He stated that they will never clean a MAF because they are to sensitive and there easy to screw up and once they fail its only a matter of time before it will fail again That being said I needed to find a NEW MAF sensor so I could get up to Rennsport . So I hit the internet looking .

So I read on and look at where I can purchase a MAF sensor and no one had one in stock. Not even the dealer would have to order it and would take a week . I was thankful to hear that once they told me the price to get one ordered and almost fell off my chair.

Saw some on eBay and looked at there location and found some with new ones near my area that I could go pick up if they would allow me to so I emailed them. I was trying every option I could think of.

Then It's now late at night and It dawned on me there was a dismantling company in sun valley that deals in nothing but porches parts. I searched there web site and they had some new ones on the site . So I e mailed them seeing if there was any way to get them to sell me one on a Saturday.
Saturday morning comes and I have am email from Peter over there stating yes we have one and it's $125.00. And we close at Noon. So I was stoked to say the least and hauled *** over there to pick it up. When I got there he let me know the new ones they just sell on line and there dropped shipped and more money. Put he still had some off low mileage good cars so I went for it.
Went home and pulled the aftermarket CAI and Installed my stock one back in after I cleaned it and new filter , this didn't take more then 30 min. Installed the New Used MAF sensor and went for a ride got on it in all gears going well over 6K rpm and " No Lights cam on and The car ran better then ever and because of removing the after Market CAI, It ran great with no more Drone sound which also made me feel better about the whole thing.
So we took off to Rennsport and had a great time and drive. with not one light issue or anything. And all is good still to date.
I would advise ordering one of these sensors and keeping it on hand . If you get in this situation like I did don't wait. Just install a new MAF sensor and be done with it. And I have to admit the stock intake for me is more responsive in the higher rpm range, I'm sure that's how Porsche designed it...Can't mess with good German engineering. The only Mod I want from this point forward is just a PSE Caustic if possible to find.
Thanks to all within this forum and hope this might help someone with these similar symptoms.
Be safe, Kind Regards