Best way to disable PSM?
02-07-2016, 02:01 AM
#1
Best way to disable PSM?
I’d like to add a switch that let’s me turn PSM completely off (or back on). I’ve found very little info on how to do this on a 996 (my car is a 996 C2), and rather more on how to do it on a Cayman, especially the 2nd generation. In all, I’ve found 7+ possible methods, below. Any added insight into what works, plusses & minuses, and how to actually do it would be greatly appreciated!
Here’s what I found in various forums, here and elsewhere. (I hope no one minds my not attributing authorship, but I’ve at least used quotes to show where I’m quoting. Google can tell you the rest.)
1. “Disconnect the yaw sensor on the tunnel in front of the shifter.” Downside: “ABS performance can be degraded (though still fully functional - depends on the system)”. (If I understand correctly, this is an unconfirmed hypothesis. But the later 996 ABS systems (version 3.5.7 I think) are more sophisticated, they brake the four wheels independently, and I can imagine they use the yaw sensor.) (There can be other dowsides on PASM, Sport Chrono, or PDK equiped cars, not relevant for 996s obviously.) This seems quite popular with 2nd gen Caymans and Boxsters, often done by putting a rocker swich on the ground wire. I haven’t found any instructions how to do this on a 996, and no terribly clear instructions re. 987s, etc.
2. Unplug “the clip going to the yellow sensor on the side of the brake fluid reservoir. … Disconnecting the sensor … did disable PSM and ABS still worked. I was able to back the car into corners at will and engage ABS. You do get 2 warning lights at start up and every ~15min for PSM failure and brake fluid sensor. It's annoying but not that bad.” Downside: No warning if you lose too much brake fluid. But assuming this can be connected to a rocker switch and one only uses it for track or drifting sessions, then one can check the fluid again at regular intervals.
3. “Interrupting power to the actual PSM computer by putting a switch on the ground wire for the module.” I found this mentioned just once, no further details. The poster said he had seen reference to this working. Downside? I seem to recall reading elsewhere that the PSM controller also controls ABS, but I could be wrong.
4. “The Durametric tool will do it or find an indie mechanic with the PIWIS tool to do it.” This is the only mention I saw of this, and it was not clear the poster had actually done it or knew someone who had. A software fix could potentially mean PSM is turned off with zero effect on anything else … .
5. Same as 4?? Napleton Motorsports disables PSM on the Interseries race Caymans by a software and/or ECU solution. Those who mentioned this suspect/hope that this desables nothing else.
6. “On a 987.1 find pin #6 on the 6-pin connector of the accelerometer. Install a rocker switch on the #6 wire between the connector and the accelerometer. Turn the rocket switch OFF before starting the engine and PSM is disabled. ABS remains functional.” I don’t think I saw this mentioned anywhere else. No clue if it’s applicable to a 996. And I'm wondering if this is similar to number 1. (Is the accelerometer the same as a yaw sensor?)
7. Disconnecting a switch under the brake pedal [another one found only in 987 forums]: "There are two switched on the brake pedal, one for the lights and one for PSM, disconnect the PSM switch and you should be in trail braking heaven." Also “disengage the PSM brake override by disconnecting the two wires at the brake pedal”. Disadvantage: Another poster said this also disables ABS. And on some cars – probably earlier ones – there is just one switch, so you loose the brake lights.
8. Pulling a fuse? This was suggested, but not confirmed in a 987 forum: “pull the 25A fuse for the "Control Unit, PSM" located in Column C, Row 8 in, I believe, the front left cabin fuse box.” Disadvantages: Loss of brake bias control. And there was a question whether this is the same fuse as for ABS which probably wan’t answered.
9. “A less complete alternative is to have someone with PIWIS code your Cayman to believe that it has composite brakes. This will reduce even more the amount of intervention when the nominal "PSM Off" button is pushed.” Again, 987 forums only – and only one mention. Disadvantage: Might it affect ABS performance? Or PSM when on?
Again, any added insight into what works, plusses & minuses, and how to actually do it would be greatly appreciated!
Here’s what I found in various forums, here and elsewhere. (I hope no one minds my not attributing authorship, but I’ve at least used quotes to show where I’m quoting. Google can tell you the rest.)
1. “Disconnect the yaw sensor on the tunnel in front of the shifter.” Downside: “ABS performance can be degraded (though still fully functional - depends on the system)”. (If I understand correctly, this is an unconfirmed hypothesis. But the later 996 ABS systems (version 3.5.7 I think) are more sophisticated, they brake the four wheels independently, and I can imagine they use the yaw sensor.) (There can be other dowsides on PASM, Sport Chrono, or PDK equiped cars, not relevant for 996s obviously.) This seems quite popular with 2nd gen Caymans and Boxsters, often done by putting a rocker swich on the ground wire. I haven’t found any instructions how to do this on a 996, and no terribly clear instructions re. 987s, etc.
2. Unplug “the clip going to the yellow sensor on the side of the brake fluid reservoir. … Disconnecting the sensor … did disable PSM and ABS still worked. I was able to back the car into corners at will and engage ABS. You do get 2 warning lights at start up and every ~15min for PSM failure and brake fluid sensor. It's annoying but not that bad.” Downside: No warning if you lose too much brake fluid. But assuming this can be connected to a rocker switch and one only uses it for track or drifting sessions, then one can check the fluid again at regular intervals.
3. “Interrupting power to the actual PSM computer by putting a switch on the ground wire for the module.” I found this mentioned just once, no further details. The poster said he had seen reference to this working. Downside? I seem to recall reading elsewhere that the PSM controller also controls ABS, but I could be wrong.
4. “The Durametric tool will do it or find an indie mechanic with the PIWIS tool to do it.” This is the only mention I saw of this, and it was not clear the poster had actually done it or knew someone who had. A software fix could potentially mean PSM is turned off with zero effect on anything else … .
5. Same as 4?? Napleton Motorsports disables PSM on the Interseries race Caymans by a software and/or ECU solution. Those who mentioned this suspect/hope that this desables nothing else.
6. “On a 987.1 find pin #6 on the 6-pin connector of the accelerometer. Install a rocker switch on the #6 wire between the connector and the accelerometer. Turn the rocket switch OFF before starting the engine and PSM is disabled. ABS remains functional.” I don’t think I saw this mentioned anywhere else. No clue if it’s applicable to a 996. And I'm wondering if this is similar to number 1. (Is the accelerometer the same as a yaw sensor?)
7. Disconnecting a switch under the brake pedal [another one found only in 987 forums]: "There are two switched on the brake pedal, one for the lights and one for PSM, disconnect the PSM switch and you should be in trail braking heaven." Also “disengage the PSM brake override by disconnecting the two wires at the brake pedal”. Disadvantage: Another poster said this also disables ABS. And on some cars – probably earlier ones – there is just one switch, so you loose the brake lights.
8. Pulling a fuse? This was suggested, but not confirmed in a 987 forum: “pull the 25A fuse for the "Control Unit, PSM" located in Column C, Row 8 in, I believe, the front left cabin fuse box.” Disadvantages: Loss of brake bias control. And there was a question whether this is the same fuse as for ABS which probably wan’t answered.
9. “A less complete alternative is to have someone with PIWIS code your Cayman to believe that it has composite brakes. This will reduce even more the amount of intervention when the nominal "PSM Off" button is pushed.” Again, 987 forums only – and only one mention. Disadvantage: Might it affect ABS performance? Or PSM when on?
Again, any added insight into what works, plusses & minuses, and how to actually do it would be greatly appreciated!
Last edited by rs10; 02-15-2016 at 03:00 PM.
02-07-2016, 03:25 AM
#2
What's wrong with the way the on , off switch currently works ?
If you turn it off it only turns on again again if you stomp on the brakes hard enough the abs activates
You can get it pretty lary easily with the switch off .
It's a good feature , even with it on , it cuts in faily late compared to mercedes and BMW systems , it's got more fun built in. The 996 system is less invasive than the system on later cars. The whole abs system is linked to the PSM , do you really want to back yard engineer the abs?
My vote would be to leave it alone and try turning it off with the switch when you want .
If you turn it off it only turns on again again if you stomp on the brakes hard enough the abs activates
You can get it pretty lary easily with the switch off .
It's a good feature , even with it on , it cuts in faily late compared to mercedes and BMW systems , it's got more fun built in. The 996 system is less invasive than the system on later cars. The whole abs system is linked to the PSM , do you really want to back yard engineer the abs?
My vote would be to leave it alone and try turning it off with the switch when you want .
Last edited by Vancouver996; 02-07-2016 at 12:52 PM.
02-07-2016, 11:15 AM
#4
On the track, while I prefer it off, even with the PSM on its not very invasive assuming you're smooth with you inputs. The switch does a good job of keeping it at bay.
02-07-2016, 01:22 PM
#5
Yes, it's quite good, and is much better than on BMW's I've tried. I know of four reasons why one might nonetheless want to switch it off sometimes: Drifting, trail braking, developing driver skills, and (maybe?) lap times. Some of these reasons interest me.
While I've seen a limited number of posts about how to turn it off, I've seen lots and lots of posts arguing whether it makes sense to turn it off. So if questions about why one would want to switch it off reflect curiosity, and if my answers don't satisfy, I'd suggest finding those threads (mainly here and at planet-9). And for those who want to provide arguments for keeping psm on or off that even those threads don't include, well, better one big thread with all the arguments than lot's of little ones. So I'd also suggest adding such arguments to those threads.
Thanks!
While I've seen a limited number of posts about how to turn it off, I've seen lots and lots of posts arguing whether it makes sense to turn it off. So if questions about why one would want to switch it off reflect curiosity, and if my answers don't satisfy, I'd suggest finding those threads (mainly here and at planet-9). And for those who want to provide arguments for keeping psm on or off that even those threads don't include, well, better one big thread with all the arguments than lot's of little ones. So I'd also suggest adding such arguments to those threads.
Thanks!
02-07-2016, 01:48 PM
#6
It might be worth talking to some drivers who have dedicated track cars on their expiriences with this.
I remember reading gt porsche magazines PSM vs non PSM track tests , the non psm car in the hands of a professional race driver was a few seconds faster around the Nurburgring .
But the PSM car was faster in the hands of club racer level enthusiasts and the motoring press
My thoughts are to use the car with the PSM turned on and off to really learn what the car can and can't do in either mode , and if even in off mode you find its limiting your considerable skills .
Then consider buying a non PSM car , or hacking the system ( probably want some expert help on this by a mechanic that track preps Porsches)
In my case , I've done level two and am signed up for level 3 race driving training , but if I'm honest about my skills , I'm not at the permanent disable PSM level , the switch works fine for my skill level , especialy on a street car that is not seeing major track time .
Button off and she can get sideways enough for big grins
I remember reading gt porsche magazines PSM vs non PSM track tests , the non psm car in the hands of a professional race driver was a few seconds faster around the Nurburgring .
But the PSM car was faster in the hands of club racer level enthusiasts and the motoring press
My thoughts are to use the car with the PSM turned on and off to really learn what the car can and can't do in either mode , and if even in off mode you find its limiting your considerable skills .
Then consider buying a non PSM car , or hacking the system ( probably want some expert help on this by a mechanic that track preps Porsches)
In my case , I've done level two and am signed up for level 3 race driving training , but if I'm honest about my skills , I'm not at the permanent disable PSM level , the switch works fine for my skill level , especialy on a street car that is not seeing major track time .
Button off and she can get sideways enough for big grins
02-07-2016, 02:00 PM
#7
Burning Brakes
Or you can hope yours just quits like mine did 2 years ago (I typically ran with PSM on; it only occasionally engaged sometimes resulting in small tank slappers). ...anyway, finished a great weekend at RA and heading out for the last session of the event and I get the 'PSM Failure, Drive to Workshop'. And that's just what I did After throwing about $2k at the issue (had my ABS module rebuilt, purchased new pre charge pump, a few other things my Indy chased) he couldn't resolve the issue and the only alternative was the dealer. I just bit the bullet and started tracking without the PSM and low and behold, my lap times dropped. This year will be my 2nd full year without PSM and I never missed it. I don't blame you for wanting to be able to turn it off for track events.
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02-07-2016, 02:42 PM
#8
RL Community Team
Rennlist Member
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4. “The Durametric tool will do it or find an indie mechanic with the PIWIS tool to do it.” This is the only mention I saw of this, and it was not clear the poster had actually done it or knew someone who had. A software fix could potentially mean PSM is turned off with zero effect on anything else … .
5. Same as 4?? Napleton Motorsports disables PSM on the Interseries race Caymans by a software and/or ECU solution. Those who mentioned this suspect/hope that this desables nothing else.
9. “A less complete alternative is to have someone with PIWIS code your Cayman to believe that it has composite brakes. This will reduce even more the amount of intervention when the nominal "PSM Off" button is pushed.” Again, 987 forums only – and only one mention. Disadvantage: Might it affect ABS performance? Or PSM when on?
5. Same as 4?? Napleton Motorsports disables PSM on the Interseries race Caymans by a software and/or ECU solution. Those who mentioned this suspect/hope that this desables nothing else.
9. “A less complete alternative is to have someone with PIWIS code your Cayman to believe that it has composite brakes. This will reduce even more the amount of intervention when the nominal "PSM Off" button is pushed.” Again, 987 forums only – and only one mention. Disadvantage: Might it affect ABS performance? Or PSM when on?
02-15-2016, 03:07 PM
#9
Looks like I will give option number 2 a try: First manually disconnecting/reconnecting the sensor. Then, if it seems to do what I want it to do, I'll try to install a switch.
I expect that in the worst case, I'll get the same result as number 1, plus when it's disconnected, I'll be without a brake fluid warning. So in the worst case, it will affect ABS performance either partly, or not at all.
Number 1 is also tempting, but for the lack of good instructions. Maybe someday ...
Number 6 also sounds interesting, and I'm wondering if the accelerometer isn't the same thing as the yaw sensor (I just added this question to the original post). Disconnecting just one wire sounds like it might only cancel some functions of the accelerometer. But lacking further info ... .
I expect that in the worst case, I'll get the same result as number 1, plus when it's disconnected, I'll be without a brake fluid warning. So in the worst case, it will affect ABS performance either partly, or not at all.
Number 1 is also tempting, but for the lack of good instructions. Maybe someday ...
Number 6 also sounds interesting, and I'm wondering if the accelerometer isn't the same thing as the yaw sensor (I just added this question to the original post). Disconnecting just one wire sounds like it might only cancel some functions of the accelerometer. But lacking further info ... .
02-15-2016, 09:56 PM
#10
Rennlist Member
I always turn the PSM off when I'm on track (except when it's wet, or if I forget to push the button
). I have never had any issues at RMP, but at Pacific Raceway somewhere between turns 7 and 8 I always feel the PSM kick in and it's a bit unsettling. The track is a lot more fun without it (and the rear brakes last a lot longer!)
02-16-2016, 07:01 PM
#11
I'm now wondering if "ABS performance can [may?] be degraded (though still fully functional - depends on the system)” is necessarily a disadvantage.
When the 996.2 was launched, it was criticized for the ABS system interfering with trail braking (which the 996.1's ABS presumably did not). So the ideal would be if disabling PSM disabled the relevant function of the ABS system, and not the rest. And if this function requires the yaw sensor, then disconnecting it might be the way to go. (Or maybe, if I'm lucky, disconnecting the brake fluid sensor will do the same.)
Of course, most of the time I'd prefer fully functioning ABS - that's the beauty of a switch.
When the 996.2 was launched, it was criticized for the ABS system interfering with trail braking (which the 996.1's ABS presumably did not). So the ideal would be if disabling PSM disabled the relevant function of the ABS system, and not the rest. And if this function requires the yaw sensor, then disconnecting it might be the way to go. (Or maybe, if I'm lucky, disconnecting the brake fluid sensor will do the same.)
Of course, most of the time I'd prefer fully functioning ABS - that's the beauty of a switch.
02-16-2016, 07:03 PM
#12
Race Director
^ I'm left wondering what maneuvers you've done that have resulted in the reactivation of PSM - and I'm not being argumentative, just genuinely curious.
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158Sierra (11-09-2021)
02-16-2016, 11:46 PM
#13
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The PSM stuff was one of the (several) reasons I prefer a GT3/2 over a Turbo, and it was a big nuisance when driving aggressively. It does not allow for significant trail braking, nor any rotation of the car while the brakes are applied (even lightly). One can drive around it, but I really enjoy trail braking/rotating a car under the brakes. That type of driving is not generally faster (though to me it can be more fun), however i could see a small difference here and there.
My educated understanding is that the “stability” part of the PSM system interferes under braking (even with system disabled via dash switch - this is what the original poster is trying to eliminate) when there’s yaw, steering wheel is not straight, or at least one front wheel is locked up. Note that on the 997, the PSM system has been programmed to intervene somewhat later, and amongst other things, requires both front wheels to be close to lock up.
In any case, please let us know what you do. I had considered grounding the yaw switch before deciding to leave my turbo alone and going with a GT3. On a regular Carrera equipped with PSM, this was my #1 complaint!
My educated understanding is that the “stability” part of the PSM system interferes under braking (even with system disabled via dash switch - this is what the original poster is trying to eliminate) when there’s yaw, steering wheel is not straight, or at least one front wheel is locked up. Note that on the 997, the PSM system has been programmed to intervene somewhat later, and amongst other things, requires both front wheels to be close to lock up.
In any case, please let us know what you do. I had considered grounding the yaw switch before deciding to leave my turbo alone and going with a GT3. On a regular Carrera equipped with PSM, this was my #1 complaint!
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thurstonpowers3 (06-09-2020)
02-17-2016, 12:55 AM
#14
Rennlist Member
It does not allow for significant trail braking, nor any rotation of the car while the brakes are applied (even lightly).
My educated understanding is that the “stability” part of the PSM system interferes under braking (even with system disabled via dash switch - this is what the original poster is trying to eliminate) when there’s yaw, steering wheel is not straight, or at least one front wheel is locked up. Note that on the 997, the PSM system has been programmed to intervene somewhat later, and amongst other things, requires both front wheels to be close to lock up.
My educated understanding is that the “stability” part of the PSM system interferes under braking (even with system disabled via dash switch - this is what the original poster is trying to eliminate) when there’s yaw, steering wheel is not straight, or at least one front wheel is locked up. Note that on the 997, the PSM system has been programmed to intervene somewhat later, and amongst other things, requires both front wheels to be close to lock up.
