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Help - PSM and ABS failure warning

P911X50

Nurburgring
Joined
3 Jan 2017
Messages
421
Help!

I took the 996tt out for an MOT today. It passed. As I was driving back I pushed the car and all of a sudden the power dropped off and the engine cut out as I was coming to a roundabout.

I restarted the car and the lights were saying PSM failure and ABS failure - drive to workshop.

I drove it back home (2 miles) carefully and parked it in the garage. I noticed that the engine was hunting and cut out?

Any ideas what this could be?

All advice appreciated.
 
Get it on a PIWIS tester asap. This will show the fault codes. I have been having fun with ABS lights coming on with my C4 which has the same brake set up as yours.

Am sure DeMort will be along soon with sagely advice.

However in the meantime, If the engine is hunting, it could be a vacuum leak to the servo, as part of my fault finding, I pulled the vacuum pipe out of the servo and this caused the engine to run lumpy at idle due to the air leak.

Further things to look at are Brake light switch, which can throw up fault codes. Fixed mine by replacing it, but cant see this making the engine run lumpy, car ran fine and then by coincidence starting throwing the ABS PASM light when I replaced master cylinder with a GT3 one from Mistercorn.

Nothing wrong with the master cylinder, however a new fault code appeared 4460 which is the ABS unit pressure sensor sending random pressure readings from 0-14 PSI to the ECU. The ECU cannot understand the readings and throws up the ABS/PASM light. In fact the DHL man has just collected my ABS unit which is heading off to ecutesting at Heanor near Derby for testing and repair.

Other causes can be wheel speed sensors (wiring is vulnerable) and the MAF sensor.

So it can be infuriating snagging this if you do not know the fault code, so suggest you get it to nearest Indy who has a PIWIS system to read it.

I have tried other systems, but they are too vague with their analysis, telling you that you have a brake system issue, but not what it is

Hope this helps (?) and dont worry you dont have to set fire to it...yet!! :) :frustrated: :frustrated:
 
Thanks Stuart,

I've changed the MAF and the brake light switch. Still have the same error codes. I've also plugged in a friends OBD II and its coming up with P1250. :roll:
 
If the engine is hunting and playing up it won't have anything to do with you ABS/PSM system. It's an engine problem. Disconnect your MAF and see how it runs once it settles down (few seconds)
 
Hi Alex,

The car runs better with the MAF disconnected. Just to make sure I connected it back up and then it started to hunt and then stalled.

Any ideas, noting ABS and PSM light are on.

Thanks
 
That code seems to be overboost detected. Have you checked that your waste gates are free to move and not corroded shut?

You have already changed the maf so this is unlikely. N75 valve may be a good shout too, as well as some boost leak checks.

If not get it to a good indy for a view.

Good luck.
 
Thanks,

How do I check the wastegate?

What does that fact that the car runs better when the MAF is removed, with the MAF it stalls (noting new MAF)?

Thanks
 
Disconnecting the MAF makes the ECU run a standard programmed in map. The ECU is getting a dodgy reading off something that's causing it to run bad. This will also trigger abs faults. Could be maf reading or an engine/exhaust sensor.
 
Unplugging a maf as said will make it run on default values .. but this doesn't mean the fault is the maf as it can mask other faults by doing this ... ie air leaks .

Your fault code is listed here but with the non standard items you have then i'm a little out of my depth and it might be more of a question for 9E to answer .

http://911uk.com/viewtopic.php?p=510426
 
Just a quick update.

Looking under the car, I found that the silicon house to the inter cooler had come off (seems the garage had not fitted it properly). I have refitted and hope its stays on. Removed codes using OBD reader and restarted the car and it all seems fine. I will take out when the weather is drier.

Thanks to everyone for your advice. Mucho appreciated. :thumbs: :thumbs:
 

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