996TT Warning Lights

[james964]

Hi
Recently purchased a 2000 996 Turbo, all was fine until today the dash has lit up with the ABS and PASM failure lights.
Any ideas anyone?

[monthefish]

If I recall correctly, there is a huge number of possible causes of this.

Did both lights come on together?
If you turn ignition off, do these lights stay off?

p.s. It's not just warning lights - you don't have ABS and PSM so be careful.

[james964]

Yes both together.

[monthefish]

From rennlist:

• ***********

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.

[james964]

Thanks very helpful but where to start?

It happened after reasonably hard acceleration and cornering if that makes a difference?

[james964]

On that list is intake air leak is it normal to hear the turbos whoosh at full boost?

[monthefish]

james964 said:

On that list is intake air leak is it normal to hear the turbos whoosh at full boost?

A bit.

What is your full boost? Should be 0.6-0.7 if car is standard.

james964 said:

It happened after reasonably hard acceleration and cornering if that makes a difference?

Does the acceleration feel linear?

james964 said:

Thanks very helpful but where to start?

Your best bet would be to get your fault codes read, before you start changing any parts. Do you know anyone with a OBD reader?

[james964]

Sounds normal then! boost is 0.6-0.7. The noise is not loud just a slight whistle/whoosh at full boost. I will speak to my mechanic to see if he has the diagnostics required. Will the fault codes show the likely problem?

[monthefish]

james964 said:

Sounds normal then! boost is 0.6-0.7. The noise is not loud just a slight whistle/whoosh at full boost. I will speak to my mechanic to see if he has the diagnostics required. Will the fault codes show the likely problem?

Most garages should have the right reader, or you could befriend your local AA or RAC man....

The fault codes will tell you the failure, but won't necessarily tell you which component has failed. Getting the codes will definitely point you in the right direction though.

Let us know how you get on.

[james964]

Thanks for your help, fingers crossed nothing too serious!

[Moosh]

most common one to fail of the list above is

2) MAF sensor

[Nobby Diesel]

Let me guess, accelerating round a right hander?

[james964]

Close. Left hander! Why?

[james964]

If it is the MAF sensor will a clean up help or is it best to replace? Also is it fairly straightforward to do?

[monthefish]

james964 said:

Close. Left hander!

james964 said:

If it is the MAF sensor will a clean up help or is it best to replace? Also is it fairly straightforward to do?

I think if it is the MAF that is the likely cause, you've got nothing to lose by cleaning it and seeing if that fixes your problem. Apparently quite an easy job (never done it myself) and could potentially save you the cost of a new one.

[Pope]

Check the little hose to the right of the throttle valve unit from the N75 valve - it's a common one that splits and causes this fault.....

Edited by Pope on Thursday 30th August 14:08

[maxpaul]

Hi
I have also had this problem with my 2003 996TT only after a remap and on max boost.
Changed loads of bits MAF and worn hoses then finaly cured it by replacing the plugs and coil packs.
Hope this helps

[EvoSlayer]

Also worth checking the brake lights, just had the ABS/PSM warning myself which turned out to be a faulty brake light switch, £9.44 + vat. Easy enough to replace if you can manage to squeeze your hand behind the vent in the footwell!

james964 said:

If it is the MAF sensor will a clean up help or is it best to replace? Also is it fairly straightforward to do?

You could try cleaning it with IPA but it's usually a complete waste of time and won't make any difference. They're simple enough to replace, all you need is a security torx bit (the one with the hole in the end) Takes around 30 seconds.

Edited by EvoSlayer on Thursday 30th August 15:49

[ninjacost]

Moosh said:

most common one to fail of the list above is

2) MAF sensor

I second that, my first 996 turbo showed same faults and it was the maf which is an easy fix

[james964]

Can someone explain exactly where it is located please