ABS/PSM Light (w/ a cherry on top)

Yes, I've read through the similar threads and realize this could be a simple as needing a new brake pedal switch ( P/N 99661311302), but bare with me.... I've posted a few times after getting my car up and running that it has had a few scary situations where I'm going around a corner and all pwer cuts out, based on everyone's feedback, I'm learning to accept that this rather unsettling and seemingly dangerous loss of power is just the nanny sensor. Fast forward... on Sunday, I started the car up, backed up and started to move forward at a low speed (less than 10 mph) and when I put my foot on the brake, the ABS engaged and my foot ratched down as ABS does. I thought it odd, and then the ABS and PSM lights went on. I turned the car off, they dodn't go away. I drove the car for a spirited drive (assuming I had no ABS or PSM) and things seemed normal until I got that scary loss of power cut out that normally only happens when I sometimes go into a particular turn. Only this time is was in a pretty straight line. Some additional info, the previous times that this odd nanny sensor seemed to go off was when the car was cold, and I just hit 55 for the first time after starting the car up and going into the turn about 3-5 minutes after start up. After that one engagement on the same turn every time, it doesn't normally do it. Now granted, the turn does have a dirt road going off the apex of it so inevitably, cars and trucks that enter the road from the dirt road are probably brinign in dirt of ravel onto the road and making it slippery. Also, I was getting that nanny sensor issue with 7 year old Yokohama Advan tires that were very hard. So, it's my gut feeling that I have a bad/overactive sensor that just went on the fritz. Do you all think that the two scenarios are intertwines? Where woudl you start to test things? My iCarSoft POR II diagnostic does not show any brake realted codes, (just the nagging one for the air pump). Thoughts appreciated.

U need a good enough scanner or durametric and datalog the abs system. It will tell i which wheel is setting off the psm. In the mean time turn off the psm or dont hit the brakes .

Just a question on the slow speed instance - were you going into / out of a driveway or other sloped surface that could have removed weight from a tire or had it hanging in the air ? If that scenario happens and you apply the brake, you will get an ABS / PSM fault. I have worked PSM out very thoroughly on my car and only very occasionally would say its intervention was equivalent to a large power reduction. The vast majority of the time, it starts intervening well before a loss of traction scenario and it's close to transparent from the drivers seat. If you go on my YT and watch track videos from early this season before I completely removed PSM from the equation, you can see the PSM working very clearly in the data overlay's. At a minimum, anytime you see WOT and a brake application simultaneously, the PSM is what is activating the brakes. It was probably working other times as well, but not something I could decipher as easily in the videos as when it's applied during WOT when I know my foot is nowhere near the brakes.

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Zbomb - thanks for the insight, this makes me even more convinced then that my PSM was not working properly. The instances where this braking/reduction of power took place were more like someone stomped on the brakes, cut the ignition, and grabbed the steering wheel. It was always a jar to the system, no where near an almost transparent assist. Sounds like your "nanny' is from the Sound of Music, and mine is Nurse Ratchet from One Flew Over the Cuckoos Nest! As to the first strange ABS instance, i really can't remember now. But I don't think there was a wheel that lifted. Regarding the track, I'd be scared to drive the car on the track with PSM on if it acted the way it does for me now. I look forward to watchign your videos.

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Thanks for the suggestion. I don't think the iCarSoft does that. If anyone knows differently, please let me know.

Sounds like you have a brake light switch problem....Two reasons I think so..... IF the brake light switch activates erroneously ( or you actually apply the brakes) ,the DME will chop the throttle on E-gas cars. It is a fail-safe of the E-gas system . The DME will not accept throttle position and brake position application at the same time, it will chose one command and chop the throttle. IF the brake line pressure actually raises(there is a sensor that monitors this) BEFORE the brake lights activate, the abs/psm fault light will come on and store a code...This is caused by a flakey brake light switch or has been knocked out of adjustment.

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Thanks for your thoughts on this. But what do you think of the following: - I wasn't getting the nanny interference with brakes applied, I was either accelerateing or neutral through the turn - the nanny interference happened for the past few months, the ABS/PSM lights just went off this weekend - I don't have any codes for this, (the only code I have is a pre-existing P0491

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Just because you were not applying the brakes at the time does not mean the brake light switch wasn't activating "by it's self". I have seen people walk away from the car and the brake lights stay on...due to a faulty switch.

P-tech theory is supported by this thread on pelican. http://forums.pelicanparts.com/porsc...lem-cured.html

I've had a similar problem intermittently on my 03 4S where if I taking a sharp right-hand turn at low speed (like from a stop sign) my car will seemingly cut power, but not with the PSM de-activated. I've noticed it more when going slightly uphill but I have a hard time believing I'm pulling a wheel off the ground, but I've thought of that too. Does that sound like the brake switch issue?

Just throwing out that I'd seriously hands-on investigate anything that @Porschetech3 suggests before I rule it out.

A durametric scanner was mentioned above - any suggestions based on actual use as to a good one for 996s? I'd like to know which wheel is throwing the brake wear sensor before I put the car on a lift and start pulling the wheels off one by one to check visually. I did the new brake pedal switch ( P/N 99661311302) fix when I first saw the ABS/PSM light come on two years ago - with zero indication it was an actual failure of ABS/PSM - and it has worked ever since. Except if I nail the brakes hard such as last week when I decided not to go for it as the light was turning a distinctly dark shade of yellow. The lights did not reappear during the course of several subsequent drives, but I continue to make offerings to the Gods of Stuttgart every time I crank her up.

To the OP: You haven't posted feedback to all the suggestions on your other thread https://rennlist.com/forums/996-foru...rnering-2.html That would be worth your while as your ABS/PSM troubles you posted here are most likely related. I saw in the other thread that it's a C4s converted to RWD. That alone could be a major factor and reason for what you are experiencing as the yaw rate of your now C2 is different from the C4S calibration inside the PSM, believe it or not. Add to that possibly different tyre sizes than the standard C4S sizes (your never listed the sizes just the brand...Go on, pull your finger out and post them) and you have another pointer. What did the check of your newly installed fuel pump installation yield? If PSM intervenes amd cuts power or brakes a single wheel an Amber light flashes. Did you notice that at any time in the corner of your eye? From your description of the symptoms regarding ABS cutting in on Sunday I would look into all 4 speed sensor signals using durametric (hobby or Pro version doesn't matter) and log those. A intermittent break in one of the wheels speed sensors while you brake will be interpreted as a locked wheel and will thus immediately trigger ABS action. It bleeds pressure from the caliper of the corresponding wheel and the pump will run to get the bled fluid back in the hydraulic circuit. That's the pulsing you feel in your foot. Help us helping you by posting the results of the checks given to you (3 alone in this post).

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Hardtailer - thanks for the post. I went back in and answered the few that I saw, but in short, the tires are stock and fuel pump seems fine (other than the issue of the tank gauge not showing full). Yes, it's converted, but in all of the people I've talked to and threads I've followed, nobody ever mentions any sort of negative affect, and a few have said that PSM is unaffected. No, there was no amber light flash in any of the times this has happened. I really do think this is a combination issue. One where the brake switch went out last Sunday and that lit up the lights. It may also be related to the jarring power zaps, but my gut feelign is it's a bad sensor at one of the wheels. I'll have to replace my iCarSoft with a Duramtric. The thing is, the power zapping issue doesn't happen under braking, it happens while accelerating. And honestly, it's such a jarring feeling, I don't know if it's a power cut out, or a brake grab. That might be hard to believe, but it happens so fast and is so unsettling that your concentration goes to safety and not "hmmm, that was odd".

Update - So I replaced the brake switch with a genuine Porsche switch and checked the fluid levels. No help. I was driving away today to run some errands and as I started to drive away and apply the brakes lightly at about 20, the ABS engaged. I'm thinking I have a bad wheels speed/ABS sensor. I tried to access the computer on my iCarSoft POR II, but for some reason it kept saying there was an error reading my ABS. It works for other things like OBD readouts and oil light resets, but kinda strange that it would'nt read the ABS. Next step is to take it into my local indy and have them plug in their Pwiz to check out the sensors. Oh, and I haven't cleaned my MAF, but I will. I just kinda lowere it on the priority list since it was replaced within 3000 miles.

Problem solved - at least I think... So even though no code ever came up, my local indy used their PWIS to check the logs for my ABS/speed sensors and they suspect the front left is bad. We will replace tomorrow. Now I'm curious to see what a "normal" and healthy PSM (nanny) feels like when needed instead of the way I've been experiencing it.

First it was personal. (I had a bad one.) But now I'm starting to really dislike these wheel speed sensors.

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Tell me about it. Expecially when you find out the cheap one (non-Porsche, but BOSCH) isn't the one you need when you have a C4... it costs double. Ugh. LOL

I had transient abs/PSM failure. Driving straight/in a corner/ or simply braking. I bought a durametric. Multiple codes. Replaced maf, recalibrate steering position sensor. Out of desperation I purchased a brake light switch. My independent shop. Installed it during other repairs. The tech checked the old switch and found the internal spring was cocked sideways. This caused the transient failure. He opened the new switch before installing and found it was cocked also. �Repaired � the new switch, installed and all has been good ever since.

SO - I went for a spirited drive yesterday and two things happened: First, i got the "nanny" activation while going around another left hand turn, but second, while navigating some swoopy S-turns with a very bumpy road, my yellow caution light came on (the one with the exclamation point in the triangle). This happened twice while in a turn and having the front dive and return rapidly over uneven pavement at about 50-60 mph. The first problem should have been fixed by replacing the "glued in" sensor, but it seems it must be something else. I guess I'll be going back to the shop. Does anyone think the two issues are related? Bad connection? Could t have been somethign to do with fuel delivery as I was down to about 3 gallons (and remember, I have a C4S with the saddle tank)? The odd thing is I just autocrossed the car all day last week and not a single light came on.

There are 2 (I think) yaw sensors in the cabin that feed data (acceleration, deceleration, yaw angle(s) ) to the ECU/ABS/PSM systems... Has your tech checked or mentioned them? I�ve had an issue with my PSM/ABS lights coming on after 6-10 miles - but I don�t have any other problems associated with the lights. They reset when I shut the car off. I do get a �steering angle sensor� code, which I haven�t been able to recalibrate (the steering angle sensor looks like a pita job so I haven�t done it yet)...

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Hi dporto - I/we haven't gone down that alley yet, but I have got an appointment next Tues to do a little exploring. Thanks for the idea.

Help please...�02, 996 turbo with 111k miles. Running fine till I blew a tire (RR) on freeway at about 85mph. Put it on tow truck. Couldn�t find another Toyo R 888...so bought a pair of Federal 295x30x18ś. Mounted and took off for home. Went into a hard left hand turn round about at 30mph...felt like full brake on RR wheel. What????...Drove to the tire shop. Looked at everything...no rub etc. Tire shop guy rode with me...could not duplicate event. This week, hard left, same circle...this time feels like both right side brakes are coming on...car lunges, goes, lunges etc. straigthn line...all is fine, no noises etc. Now ABS and PMS light on What to do?

The correct scanner can read the abs inputs while driving and tell u if they r kicking on or faulting the sytem. Chances r u need to replace 1 or more abs sensors. In the mean time turn off the psm as its "locking" the wheel down.

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Mike - This may be a shot in the dark, but it ends up one of my problems was an ABS sensor that was poorly mounted and I think it was throwing codes. I�m wondering if when your tire blew that it either knocked a sensor or damage the wires going to it and that could be causing her problems.

Update - my local Indy suggested I go with a a full 3 litre bleed (activating the ABS to purge bubbles) and replace the remaining three speed sensors. I went with the first suggestion and took the car to the track this weekend. The ABS/PSM lights did not go off at all. That being said, I did still get the "CAUTION" light (the yellow triangle with the exclamation point in it) go off over a harsh bump and dive situation at close to 100mph. This was a similar situation to my backroads driving. I think I'll start chasing down loose connection and start with the battery, then grounds. ANyboady have any other suggestions on what to chase after that?