When you disconnect the pre-charge pump it shutsdown the PSM right away and you will get the message PSM failiure, ABS will be fully functional when you do this.
You will have no interference at all from the PSM.

 

I'm trying to figure out what causes this problem and I have a few questions.

• What tire size did you use when this happen
• Whats the lock rate of your LSD?

 

Anyone ever had this problem while using upgraded GT3 calipers and discs on their turbo?

 

Kanon, tack för tipset!
(Great, thanks for the hint!)

 

If this question was for me, from my side it was pretty clear that when I have pretty much rear-end steer around hairpins, or at switchbacks from one side to another that gives the car a bit of transition/corner entry oversteer and me sometimes having to catch that with a bit countersteer, "core PSM" would interfere. I ran GT2 wheels with only difference 245/40 front tires instead of OEM 235 (so slightly larger diam). The diff lock is 50% on decel.

I did not feel it was unexpected at any time from PSM, or wrong either from PSM, it would be necessary to save the driver from a classic 911 spin out if this action was not fully intentional.

If now, as fellow Swede Speedfreak posted, the complete PSM function, incl PSM core function, is gone with the pre-charge pump disconnected then my problems are solved.

But I tested the car with 1 PSM fuse pulled out, that kept the ABS working and put the PSM failure light on, and it took three tailhappy turns to have core PSM go off again. I will check with a meter if this was the pre-charge pump fuse (it only says PSM in the fuse plan).

 

Im, sure if the fuse is pulled that it disables both PSM & ABS... I haven't tried SpeadFreaks method as yet (was going to soon, just to see what happens) but I have not encountered these braking issues... I wonder if this has anything to do when brake fluid is boiled within one caliper!!!... lets face it the stock cooling isn't great under there and I run separate cooling hoses along with the Cup ducts, it does make a difference.

 

MrWhite, thanks for your input.

 

Overall, this is a very RARE problem and I think smoother braking solves and helps but still this kind of thing should not exist. I am happy now as the improved yaw rate sensor (with all kinds of other tricks I tried along the way...) helped me. However, it is "good" that after some years some other members have commented about similar problems, as I was alone hitting my head against the wall quite a bit.

Back in the days I tried without ABS/PSM and the problem still existed.

Speed's recommendation of completely disabling the PSM is very good.

Just for all the members to know, now when you press PSM off it is off BUT it comes on if your tires are sliding over 7% and you are on the brake pedal (quite good feature for amateur drivers; PSM helps when you are in problems and you try to slow down the car, however, this brings additional problems with trail braking etc. and I believe this is the reason why a lot of 997 guys have had problems with rear pads and disks. Heck, even for me rear disks last only a season )

Good stuff again MrWhite, you remind me a lot of my favorite professional racing driver who is friendly and co-operative yet very knowledgeable.

When I talked on the previous message about Turbo's ABS not being suitable I did mean ABS including the PSM. So you are right with these comments again. The car I drive is one of the first Turbos ever rolled out from the factory (car was already on the streets of Finland in the beginning of June 2000). After that (do not know the date of change) Porsche changed the yaw-rate sensor which is a critical part in the system.

The part number for new "rate of turn sensor" is 996.606.145.00 and it can be only combined with the newer hydraulic unit 996.355.955.58 (there has been two previous units with same part number ending .51 and .57. The previous rate of turn sensor was 996.606.147.00 and they look different.

PM me if further instructions are needed as I have some handy files available.

I know this question is not pointed to me, but I want to emphasize I had this problem with stock sized tires and also with tires with a minor yet accepted difference (such as 235/295), LSD lockup 45%.

Cooling is very important in all brake related issues. I am very sure proper cooling helps even in this problem. However, I tried both Motul and Castrol racing fluid along with Cup ducts and still had the problem. Perhaps that was not enough but I think it should be.

 

Just another note on this, I can definitely 100% for sure confirm that dis-connecting the pre-charge pump kills the PSM completely, however still leaves a fully functional ABS system to drive with.

Also, when plugging the connector back in, there are no active failure codes in the car and the PSM and ABS warning lights are off (and the system is back on) - could be good to know for those who don't have a code reset tool.

Additionally, driving a full two days with the pre-charge pump disconnected, on 265 fronts and 315 rears, hot day as well, I had absolutely zero braking problems this time. The car could also slip and slide in any way I wanted to with no interference from any type of "core" PSM.

Thx Speedfreak again for the input.

ANOTHER NOTE: This above, does not suggest the final solution of the OP issue reg a brake problem on Nurburgring.

 

I feel that the ABS locks the brake too much at low speeds in contrast with the OEM front brakes, it looks like the ABS need to be updated...if some one have some imput I will appreciated!

...but at high speeds the GT3 calipers work fantanstic compared with OEM and ABS locks as OEM.

I am thinking to upgrade the rear ones.....has someone some info abbout? ..is it worth?

 

Thanks for the info! Great stuff.

 

Great info for those who are heavily tracking their Turbo. I experienced this PSM issue on our shop car at Roebling Road last weekend. 2001 Turbo, around 550hp, rwd. PSM was "off" the entire time, but would come on abruptly mid corner with trail braking or light brake application.

I pulled the PSM relay as pictured in Speedfreak's post on page 3 and I'm pretty confident that this is the fix based on what I'm reading here and elsewhere.

 

This is very interesting. I have never had a problem with this mystery brake fluid level warning and the red brake failure light on the dash showing up on the street or at the track. I have always kept my fluid precisely at the Max arrow. Before the last track event, however, I did a brake fluid flush but this time slightly overfilled the reservoir to about 1/2" above the Max line. I figured, I little extra can't hurt, right? On the third session when exiting a hard right hand turn, I received the brake fluid level warning notice in the display along with the small red circular brake warning light in the dash. I could erase the notice with the stalk but the red light stayed. When I checked the fluid in the pits it was full. Once the car was shut off and restarted, the both the message and light went away and did not return during the following session. I wonder if actually having too much fluid in the reservoir may have been the culprit. Had to believe though. Does anyone have any more insight to this? Is there some king of a float type level sensor in the reservoir that can go bad?

 

Finally pulled the plug (literally)! Since I had my last alignment done with a little more aggressive settings, my PSM sometimes kicked in when taking sharp turns with higher then average speed. I tried switching off the PSM but it still came in once awhile. I finally pulled the plug as stated on page 3 (picture). You do get the PSM OFF warning light + the dashboard warning (which can be turnned off). So far, the car is driving fine.

 

How do you turn off the dashboard warning, I've just been driving with it on.