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!

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 .

I have gone into a all out spin at about 80mph with PSM off and I just use the switch. Does it really kick in when you turn it off?

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.

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!

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

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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I had a durametric, had a PIWIS1, and currently have a PIWIS2 and on a 996 I see no way with the capabilities of these tools to disable the PSM via a coding change. Not to say it cannot be done with some other tool or different model (like a Cayman), but with the factory tools I do not see that being an option.

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 ... .

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Let us know how this works out for you. I might consider doing the same. 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!)

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.

^ 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.

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!

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Thanks! Great explanation. You put what I was feeling into words.

[Image-only post; no author-written text. Original image references:] https://rennlist.com/forums/images/smilies/smile.gif

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Did you by chance find it? Or do you know how to access it? I searched the PET for "yaw" "acceler" and "sensor" and found nothing like a yaw sensor or accelerometer :-(

I don’t recall, shame. I would really appreciate it if you would update this thread if/when you move forward. Thanks.

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I started to write an answer, and it started to become a question ... . Anyway, I'm not sure I have. I haven't tracked this particular car yet (and no, I'm not in a rush to turn off PSM the first time I do). Nor have I attempted drifting it yet (which, on the other hand, I am eager to do before winter ends), for many reasons (including believing that even with PSM "off", it wouldn't let me). But is this true? Until a few weeks ago, I thought so. Amoung other things, I recall recently reading somewhere that it triggers when the car senses sufficient g forces (which seems odd, so I assumed the author meant yaw angles). But in reading how to disable it, I don't recall this being confirmed. Maybe mentioned (not sure now), but certainly not in detail. On the other hand, it seems fairly well established that if one (front?) wheel triggers ABS, PSM will come back on. Is this the only thing that will make it come back on? Can I go drifting without diabling it (if some more snow would kindly fall)? (Don't worry Ahmet, even if I can drift, I'll still try disabling it sooner or later and post what I know. But it would be very interesting to know whether something other than locking a wheel can trigger it while turned "off".)

Interesting PSM article from a racers perspective http://www.deter.com/porsche/PSM.html

My experience: With PSM disabled using the dash switch and you�re NOT on the brake pedal, no intervention, period. You can spin the car 360 degrees, do on throttle drifts, pitch it sideways and whatever you want, and it wouldn�t do anything unless you touch the brake pedal in which case it�s fully and completely active until you let go of the brake pedal and/or the car is no longer under a condition that triggers PSM intervention - more on this shortly. My educated/researched -and to the best of my perception- thoughts on STABILITY intervening requirements (while system is disabled through dash switch) are that: You must be on the brakes (even lightly), and one of the following: Yaw angle sufficiently high, At least one front wheel at impeding lock up. To further expand on why one would want to disable the PSM such that it does NOT intervene at all ---> In a nutshell, if you want the car to rotate under braking. You might want this to tidy up the line into a curve or a mid curve yaw angle adjustment (possible small performance benefit, if you have the skill). Or, you might want to get the tail to come way out under brakes, to then transition to the gas pedal for a long drift, or mid drift adjustments (certainly slower, no performance benefit what so ever on a paved surface). In either case, for me it was for personal preference. *One of my 996 turbos intervened far earlier than all the other 996s I've owned or otherwise drove or rode in a setting that would potentially trigger stability intervention. I�ve been tracking and instructing for a long time so these included a 2003 C4S, two other 02+ turbos and several 02+ Carreras, so I believe that particular turbo had a faulty yaw sensor as best I can tell. Less likely but possible that the steering angle sensor was not calibrated correctly or otherwise faulty. I mention this in case somebody reading this post finds PSM entirely too intrusive, while others do not. When everything is working properly and the system deactivated through the dash switch, you must push the car hard before you�ll feel the intervention. This isn�t like a late 90s or early 2000s �normal� car, which are entirely too intrusive, even on the street.

Great article about PSM. Maybe I'm just too aggressive through turns 7/8 Seriously though, I think it's the trail braking that reactivates the PSM, which then interferes with my driving style. What's wrong with a little slide around a corner? It can really help to rotate the car into the direction you want to go.

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I can confirm this. I recently did an autocross that was used a lot of a banked oval and subsequently had a decreasing radius turn. This is where I'm used to using heavy trail braking, drifting the car in under braking. When I tried it in my 997 with PSM "off" (liers), it was an understeering nightmare. So I'm looking for a way to disable it for track days. I saw mention of putting in a switch on "the ground wire" of some brake cable (???). Can anyone point me to a thread that talks about it? I'm Googling in the meantime...

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10) buy a 996 without it Anyway, not a crazy driver here, but it is fun to kick the rear end out a little whne it's wet and have fun with it. Dry pavement I'd never come close to needing it for almost all the stuff I do.

Any updates on this?

Not really. I did unclip the brake fluid sensor and sure enough, lots of warning lights came on. And probably I could get the rear a bit looser too. But shortly after doing so, I found myself heading off for a long highway trip in the rain, so I clipped it back in. And it was a bit of a pain to get to, so I decided not to unclip it again till I had a chance to play with the car in appropriate conditions. Hopefully I won't have to wait more than a few months, and hopefully I'll remember to post an update. Feel free to remind me, though ...

I've always assumed I never had PSM because there is no button on my dash. PSM wasnt standard in 01, was it?

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I think PSM is always an option and not std.

The Bentley book says PSM was standard on C4 from 1999 and optional on C2 from 2000. I don't know if this is a reliable source for this.

I've had some butt clenching moments in the canyons and no button. I'll just assume no psm. hah.

Bumping this thread. I've been running "option 2" but I'm looking for a better solution, one which doesn't result in what I call "over active ABS syndrome" my ABS triggers far too easily and often. Has anyone tried wiring a switch to the yaw sensor or the PSM computer? Any write ups? Thanks!

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I have a switch on the pump wiring (GND, IIRC). Switch is located inside the cabin. Switch set to OFF, PSM will be permanently off until car is restarted with switch set to ON . There will be a warning on instrument cluster, which can be removed with OBC stalk, but it will reappear after 15-20 minutes drive and can again be removed. Just nuisance, one will get used to it. ABS stays on all the time. Write up? No, but I cut the wire close to PSM unit, soldered extension wires (used shrinkable sleeve w/glue over solders and sleeve over wires) and pulled them to cabin through grommets. Switch is partially hidden under the dash (I have ClubSport center console delete) with HI/LO boost switch. Both switches UP = street boost and PSM on, DN= track boost and PSM off. =D

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And just to confirm, your ABS still works as it should? Has anyone tried cutting/adding a switch to the brake input going to the PSM unit. On newer cars there are two brake switches, one for the lights and one for PSM, disconnect the one to the PSM and it never knows that you're trail braking and PSM stays truly off. -Dino

I recently did an LS swap on my 2002 996 and since then the PSM and ABS lights have been on. I got a Durametric and found I had code 5525 "Incorrect data transfer with DME master control unit" which isn't too surprising since the DME has about 12 fault codes related to the engine missing. With just this code it seemed like the ABS wasn't working, though I wasn't able to confirm that. I tried disconnecting the yaw sensor in the center console. That gave the PSM two additional error codes, but the ABS definitely works. I ended up plunging the yaw sensor back in, but I don't think the codes cleared, since ABS still seems to work. My next steps are to check the codes again, clear the additional codes if they are there (5525 can't be cleared). Then I will confirm for sure whether the ABS works. I wanted to share, because if my hunch is correct, disabling the yaw sensor can't be done with a switch on the 996. Since you would have to clear the codes before everything goes back to normal. I'm really looking for a way to disable PSM, but have ABS work and the ABS light go out. If the PSM light could go away too, that would be ideal. Has anyone swapped the whole ABS system from a non PSM car before? Might be too much work.

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I am still new to this P car owners group. Last week after a light rain and an empty parking lot I decided to play with PSM on and off. I thought the C4S would still track pretty straight. After a few 180s and a 270 spin I realized it was fun but I like PSM. It keeps an old man with slower reflexes out of the weeds.

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5525 lits when MAF is bad or disconnected, ie there's no torque data passed to PSM computer from the Motronic. Most likely you will not get rid of it (b/c the conversion), but completely disconnecting PSM's electrics plug you'll only get the warning I mentioned in my previous post and your ABS will work. Changing the complete ABS/PSM unit to bare ABS is possible, but in order not to get any ABS/PSM related warnings you'd also need to change your instrument cluster to one matching the ABS unit. '02 car has CANbus, so that leaves only few options on the table, GT2 and GT3. Both cars have CANbus but no PSM. BUT different Motronic and engine. Motronic may not have here any effect at all, but with that engine/instrument cluster combination you'd loose at least oil level measurement (if applicable with your conversion). If your car is C4 (or C4S), then your fuel level measurement system would be similar to new cluster's and would still work. Complicated? Yes. BTDT

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I confirmed that the codes from unplugging the yaw sensor don't clear when you plug it back it. But I was wrong about 5525. I confirmed ABS does work with only that code. You are saying on a 2002 C2, if I unplug the PSM module, the ABS will still work, the ABS light will go off, but the PSM light will stay on? I should definitely try that. Thanks for your insight!

Andrew PM me, I believe I can help you out with the PSM system.

At PCASDR's performance driving school, I drifted the entire circumference of the skidpad during the throttle steering exercise. It was no 2,000HP Supra drift, but it was drifty enough that folks were applauding and taking video. When I first got the 996, I was bound and determined to get rid of PSM because it was firing off constantly. After moving from 19's with rubber band wheels to 18's and adjusting the coilovers a bit, PSM seldom interferes, and my urge to tear out the ABS pump has subsided.

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I can't PM you for some reason. I'm still interested in learning more about the PSM system. You can find me on Facebook if that's easier. Thanks.

call me, I left my number on my profile temporarily

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Interesting, I didn't know this would impact the system in that way. how did how did changing wheels and suspension do that for you? What wheels and tires did you settle on?

So has anyone tried pulling fuse? According to the fuse box diagram both Fuse 8 and Fuse 10 on Row C are related to PSM, I wonder which one (or both) should I pull? https://www.porscheclubgb.com/forum/...rQdl8y_6URGR6E

Easy enough for me - disconnect the electrical connector to this pump. PSM will be disabled and ABS will continue to function. For a track car I would highly recommend disabling PSM, the switch in the cabin does not fully disable in my 03 - this is verified with data confirming PSM activating brake application while on throttle with the switch in the off position.

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does this apply to 997? This is in the trunk with the liner removed?

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Bumping an old there here! Also curious if anyone knows if this would work on a 997.

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I added a rocker switch to cut off the yaw sensor on my 997, which does make getting the rear end out easier on skid pad.

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oh interesting! Any issues with the ABS?

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abs still work but lose sports/sports+ setting for car with sport chronouse and pasm