jury_ca

On my '03 911 Turbo. 20K Miles.
Stock airbox, lowered with Bilstein sports suspension, factory wheels and tires.

Symptom: PSM/ABS failure drive to workshop. Appears consistently accelerating rapidly up to highway speeds with boost at 0.6-0.7 bar (non WOT-condition). Light resets whenever the ignition is switched off and back on.

Searching the forums the possible causes for the ABS/PSM failure mode, drive to work shop appear to be:

1) Failing alternator
2) MAF sensor
3) Intake air leaks
4) ABS sensor
5) Pinched wiring harness from a lowered vehicle
6) Steering angle sensor giving incorrect readings after lowering

I think I can rule out 4-6 since it does not appear when braking or cornering but only under brisk acceleration.

I know I have a weak alternator that puts out just above 12 volts. My car is getting the alternator replaced on Monday. I will have the dealer read the trouble codes at this time. Car also seems to bog at low speeds and have slow throttle response and rough cold idle, so I am thinking the MAF is triggering the faults rather than the weak alternator, since I am still getting above 12 volts.

Questions:
1) Is it worthwhile to replace the MAF sensor with 996.606.125.01 before getting the codes read at the dealer? It's a simple DIY procedure which I can do on my own.
2) Is this the right sensor to use? I know some of the earlier turbo cars came with the 996.606.124.01 which is more prone to failure from dust and dirt. There has been some suggestion that the ECU needs to be reprogrammed for the newer "125" sensor.
3) Should I get the techs to check for boost leaks? The turbos peak at 1 Bar, and it seems to be able to hold 0.6-0.7 bar under load, so I feel like I can rule out boost leaks.

Kevin

What makes you think that "there" is a different MAF for the 996TT?

Installing a NA MAF will NOT work!

Are you running a stock filter?

Replace the Alternator and have the techs check the idler pulleys.

Replacing your MAF with the correct turbo MAF is always a good thing!

The MAF controls your fueling and boost...

jury_ca

I am running a stock filter. There is an updated MAF for the turbo cars:
http://www.vividracing.com/catalog/p...e-p-45758.html

I have seen some posts claiming that the ECU has to be reprogrammed for this newer MAF but I'm not sure that this is true.

Kevin

You are starting to drink the cool aid..

Keep the stock MAF.

jury_ca

Are you saying that 996.606.125.01 is not the right MAF sensor for Turbos?

Kevin

I am saying 100% that the 996.606.125.01 is NOT to be used with your car.

Purchase the 996.606.124.00

I have them on the shelf and can save you a few bucks over the dealer.

slant911

Do what the guru Kevin says! He won't steer you wrong.

jury_ca

This morning I started the car and started to drive it out of my garage. The car started normally, and drove for about 40 feet. After about 20 seconds, the engine started sputttering and idling at 500 rpm. I switched it off and restarted. Same thing. Engine would start and run normally for about 2 seconds before the idle would drop precariously. I disconnected the MAF and started it once but it seemed to make no difference. Called the dealer to make a service appt and they suggest it could be a MAF or throttle body. Another poster on 6speed having similar symptoms found that it was the alternator. (Post #14)

http://www.6speedonline.com/forums/9...hts-again.html

I know my alternator is not putting out enough juice and was due for a replacement in 5 days anyway but the dealer is going to diagnose the stalling issue also. I was really leaning toward the MAF being the problem because of the bogging issue at low speed and the fact that my alternator voltage is still consistently above 12V (might be an amperage issue though).

dantzig

If you get the codes read, you should be able to stop guessing.

I also agree with slant911 - Kevin is seldom wrong in his diagnoses.

Kevin

The stalling ISSUE is a DEAD give away.. Replace the MAF... It is a sensor, it's very fragile and they need to be replaced every 3 to 4 years depending on your driving style and climate..

It's like asking your dealer to change the oil but you "think" that your oil filter element is good..

In the small scope of things, its a cheap tune up.

Have you relaced your plugs and with Bosch FR6LDC? New 997TT coil packs?

jury_ca

Here's a partial resolution of my issue to add to the tribal knowledge of this forum:

1) The stalling issue was caused by a failed fuel pump / venturi tubes. Replaced both and my car now starts and runs fine.

2) Replaced MAF sensor - Car no longer hesitates or surges before boost kicks in

3) Replaced alternator - Voltage gauge now reads at 13V rather than just above 12V.

4) Did a full service and replaced the plugs and belt

5) The shop I took my car to for the other work stated that the computer registered a fault code for a boost problem but they did not have time to diagnose and fix.

I think this is the cause of my PASM/ABS failure lights when I accelerate on the highway and achieve sustained boost for longer than 3 seconds. Any idea what could be failing? Bad diverter valves? Intake air leak?

Mr Michael B

PSAM/ABS fail lights can be connected to a fault where the battery vent fumes are corroding/effecting the wire harness to a front speed sensor at or near the exit of the vent hose. This has been discussed before, and even recently on 6speed. Please search for it.

adam_

I'd love to hear what the dealer charged for this...so I can point out to my wife how much money I save that I'm using for the KW v3 suspension!



Thx for posting the resolution. Your 'shortly after starting issue' made me think fuel/fuel filter, BTW

A

tracke30m3

I had the same symptoms, though my ABS / PSM lights would usually come on after jumping on the brakes after hard acceleration.

The engine would run rough and would even stall at low speeds, it also seemed to have lost lots of power and had lots of lag.

Changing my MAF didn't help and I was getting frustrated in trying to sort out this issue since there seemed to be a million things that could cause the ABS / PSM lights to come on.

One day my alternator suddenly dies and while the car was at the shop for a new one, the mechanic discovers that one of the intake hoses was missing a clip and had an incorrect seal ring. After the new alternator, seal ring and metal clip, the car now runs perfectly.

Though I'm not sure which (the alternator, seal ring or metal clip) solved the problem, this bit of info might be useful.

I find it annoying that so many different issues could cause the same warning lighs to come on, makes trouble shooting confusing and difficult.

jury_ca

My car is back in the shop to get the PASM/ABS failure diagnosed. The service advisor says that they have found an issue with the left vacuum control capsule (P/N 996 123 115 71 superceded by P/N 996 123 115 72).

I have done a search but this does not seem to be a common failure, although I suspect the fact that the P/N has been superceded indicates that the part has been redesigned for greater reliability.

Anyone know what this part does and whether this could be the cause of my engine occasionally stumbling at idle to the point that it sometimes stalls, PASM/ABS lights under boost for a couple of seconds?