What's new
Porsche 911 UK Enthusiasts Online Community Discussion Forum GB

Welcome to the @Porsche911UK website. Register a free account today to become a member! Sign up is quick and easy, then you can view, participate in topics and posts across the site that covers all things Porsche.

Already registered and looking to recovery your account, select 'login in' and then the 'forget your password' option.

Design 911 supply Porsche parts, Porsche spares and Porsche accessories, to both retail and to the trade. Our Porsche product and accessory range includes brakes, exhausts, tyres, wheels and Porsche panels and interiors.

PSM Safety Issue - Anyone Got A Systems Diagram?

P

poppopbangbang

Nurburgring
Joined
25 May 2015
Messages
480
Here's a good one, sweeping corner trail braking into the apex saw the PSM activate which resulted in one front brake locking on and a shed load of understeer. Post corner it took a good few kicks of the brake pedal to get the caliper to release.

Luckily this was on the circuit not a B road or it would have been Porsche in Ditch time!

ABS Activation doesn't recreate the problem even at high speeds and long periods of ABS activation but the problem is recreatable with PSM activation.

Does anyone have a systems diagram here that I can try to work out the failure mode? Immediate thoughts are a one way has failed somewhere and it's back pressuring the master!

Only fault code showing is a pressure sensor failure.

Obviously rather a big safety issue so I'll share any findings for future reference.
 
Check your sensor and reluctor ring on the opposite wheel, same axle.
 
alex yates said:
Check your sensor and reluctor ring on the opposite wheel, same axle.
Click to expand...

100% not that as I log individual wheel speeds, that's how I confirmed which wheel locked up and how I've validated it is not happening under ABS, no matter how small a lock (i.e. brake pressure is lazy to come off the wheel). I did this check as it's not uncommon for corrosion or debris to block a valve in the ABS valve block which results in the wheel staying locked up after the ABS has ended activation. However on mine it is definitely only happening under PSM with the brake pedal "stiffening" accordingly.

Would a grubby wheel speed trigger really spoof it? If so that is pretty terrible system design and very un-Bosch like :lol:
 
My left rear reluctor ring split and it caused my right rear caliper to keep actuating and the car juddering, disc overheating etc without even going near the brake pedal.

Don't forget it was the 1st version of PSM on the 911 so probably was pretty naff.
 
It appears to be the booster pump (or pre-charge pump as it appears to be called in the Porsche book). With it unplugged all systems work (aside from PSM) as they should with zero issue or drama (even getting into the brakes at over 1G lateral). With the pump reconnected 0.15G lateral and 10 bar of brake pressure is enough for it to pressure up the front brake circuit.

When provoking the fault code 4460 is logged which reports back as pressure sensor failure or value implausible, I think this is because there is still pressure reading when it should be zero because the pump is back feeding the master.

I have a spare on the way so will change it and report back.
 
Cool. Will be interesting to find out :thumb:
 
Proved today - with a different booster pump fitted but everything else identical the problem isn't there regardless of what slip angles and brake pressures you generate.

I'm going to dissect the old pump to see what the failure is!
 
:thumb: :worship:
 
Love these posts where the answer is found!
 
You must log in or register to reply here.

Similar threads

T
Boxster S 986 spongy brakes
Replies
5
Views
858
½cwt
Â
B
911 Brake fluid flush
Replies
14
Views
1K
Monica911
M
D
2005 PSM failure
Replies
2
Views
4K
deMort
D
S
PSM Failure Workshop dash message - Code 1435
Replies
6
Views
5K
deMort
D
spongebob squarepants
Goodbye Herman yellow, hello Herman white. Updated with pics
5 6 7 8 9
Replies
122
Views
28K
jonttt
jonttt
911Time
911Time's Project 991 - TracTive Coilover Installation
2
Replies
16
Views
2K
diceman
D
D
981 Heater issues.
Replies
4
Views
4K
Slayer
Slayer
Passion for perfection Porsche Car Sales

Latest posts

New Threads

Porsche Model Range

Porsche 911

Porsche 992: 2018- Porsche 992: 2018- Porsche 991: 2011-2019 Porsche 991: 2011-2019 Porsche 997: 2004-2012 Porsche 997: 2004-2012 Porsche 996: 1997-2005 Porsche 996: 1997-2005 Porsche 993: 1993-1998 Porsche 993: 1993-1998 Porsche 964: 1989-1993 Porsche 964: 1989-1993 Porsche Carrera 3.2: 1983-1989 Porsche Carrera 3.2: 1983-1989 Porsche Carrera SC: 1977-1983 Porsche Carrera SC: 1977-1983 Porsche 930 Turbo: 1975-1989 Porsche 930 Turbo: 1975-1989 Porsche Early 911: 1964-1977 Porsche Early 911: 1964-1977

Porsche Hypercars

Porsche 918 Spyder Porsche 918 Spyder Porsche Carrera GT Porsche Carrera GT Porsche GT1 Porsche GT1 Porsche 959 Porsche 959

Other Current Porsche Model

Porsche Taycan : (2019-0%) Porsche Taycan : (2019-0%) Porsche Macan : 2013- Porsche Macan : 2013- Porsche Panamera : 2009- Porsche Panamera : 2009- Porsche Cayman: 2005- Porsche Cayman: 2005- Porsche Cayenne: 2003- Porsche Cayenne: 2003- Porsche Boxster: 1997- Porsche Boxster: 1997-

Porsche Legacy Models

Porsche 928 Porsche 928 Porsche 968 Porsche 968 Porsche 944 Porsche 944 Porsche 924 Porsche 924 Porsche 914 Porsche 914 Porsche 912 Porsche 912 Porsche 904 Porsche 904 Porsche 550 Porsche 550 Porsche 356 Speedster Porsche 356 Speedster Porsche 356 Porsche 356

Forum statistics

Threads
124,559
Messages
1,441,513
Members
48,973
Latest member
mkrt1972

porsche insurance porsche parts porsche sales porsche car sales porsche for sale
porsche classic sales porsche tuning porsche sold porsche specialist porsche engine rebuilds porsche driver training porsche car sales porsche exhausts

Community platform by XenForo® © 2010-2024 XenForo Ltd. XenForo theme by xenfocus

www.911uk.com @Porsche911UK THE DEFINITIVE PORSCHE FORUM Copyright © 911UK 2002-2024 All rights reserved.

911uk.com is not associated and is wholly independent of Porsche Automobil Holdings SE, Dr. Ing.h.c.F.Porsche AG, Porsche Cars GB, its subsidiaries and offical Porsche centres. Any word, phrase or graphic that in any way resembles anything to do with the Porsche name or organisation are registered trademarks of Porsche Automobil Holdings SE and Dr. Ing.h.c.F. Porsche AG.

Back
Top