PSM / ABS failure drive to workshop...
 

this has only just started happening BEFOREi replaced my pads.

It went away for a while but now its back again, everytime i brake these 2 warnings light up and disable traction and abs :(

Ive read that it could be MAF related and unplugging it and then putting it back on then restarting the car seems to work for a few pumps of the brakes but then message comes on again?

Is there a sensor i need to replace?

Cheers

If it happens only when you brake, it's probably not the MAF. That stupid ABS light comes on for all kinds of stuff, but in this case, it may actually be ABS related. I'd take all the wheels off and have a real close look - or take it to the shop.

Take to shop lol ! i dont fancy being out of pocket at moment.

We had all wheels off other day to do the brake pads all round but it wasnt a real issue then.

Yes only occurs when i brake :( sometimes i can be fine for 50 miles then next time the psm and abs disabled for ages :(

Have same issue although I don't think mine is brake ( or brk lite switch ) related. Maf changed recently also so .. Who knows..
Theres a lot of threads here and other sites. Pretty common ( another ) issue it woud seem. I drove hard in fog this AM trying to replicate the dash lights coming on but not able to. Also spun wheels on freeway onramp at WOT ( new ps2's rear! ) And psm workin fine it seems.

I need a Duramteric but not Mac compatible! Argh.

I dunno about you, but CEL's ruin my day.

Could be the speed sensors on the wheels or the wiring harness that goes from the speeds sensors to the ABS/PSM unit. Their have been a rash of failures of these harnesses recently according to my mechanic. They will cost you about $475 from pelican to replace them all and then another $400-700 in labor depending on your mechanic's rates.

Hate to say it, but it's a strong possibility. Had to just do this job myself. You do not want to be caught out needing ABS and it failing on you.

Even worse could be the ABS unit but that is highly unlikely.

But I would definitely explore all of the other options first:

- MAF
- Dirty wheel sensor (clean them off)

i had the same problem in my car, and the problem was the tires, i changed for a new set Yokohama Advan but was smaller then the normal...

I changed again for yokohama A048 and the PSM/ABS light cames off, everything is normal again.....

That's relevant to me since I just put on 315/30/18's while running the stock 225/40 front and got the psm/abs take to shop CEL's the next day. So not believing in coincidences my first thought was the tire size differential but my inquiry re tires/sizes all confirm that with Michelin ps2's running those sizes on 18's is within spec?! ..So.. Off to have code(s) read.

Has anyone ever had any issues running 225/40 against 315/30's??

I've had this 3 separate times for 3 separate faults.
Just changed front left speed sensor, but previously had to change wiring harness to speed sensor ( repair kit available from Porsche).

However the first time I got the fault may be of more interest to you as it only occurred occasionaly under braking, this was the brake switch located under the brake pedal. A cheap and easy fix.

It's worth getting the fault codes read.

+1
No only worth getting the codes read out but is essential. You cant chase this problem until you read out any codes.
If you haven't invested in a Durametric then its about time you invested in one, really you should, worth their weight in Gold.
:)

Wiring harness on my 03tt had a few pins that were not making correct contact and just needed to be pushed in and or better secured. I guess going off track sidways into a bunch of powder dirt/rocks tends to shake some stuff loose on the car as well as dirty the hell out of the interior with windows down.

Luckily the issue first showed it's ugly head when my mech came to pick up the car. ABS/PSM failure is what it read and then stayed on display for quite some time until you turned the car off.

I think I had to pay around $600 or so just for the labor of getting to the area and re-securing the harness and pins. Took quite some time for it to be figured out by my tech lots of diagnosing.

You need 235/40/18 for the front to be compatible with the 315/30/18 rears. This is also the standard GT2 tire sizes from the factory.

thanks for the input. i'm aware that this is optimal for the car on stock wheels. i'm just trying to figure out ( with great difficulty! ) if although the 225/40 on the front is not optimal, it is in fact within the 3% as given to be "acceptable" by the manufacturer.

this is my dilemma. the revs per mile are 829 on the 225/40 ( diameter is 25.1 ) and revs/mile are 817 on the 315/30 ( diameter is 25.5 ). is there anyone here that can deduce from these numbers the actual % figure i am off?? if i am figuring this correctly, i have a .4 inch differential between the front and rears as they are currently? and that is within ( and yet, i understand NOT optimal ) but recommended specs for our cars. esp given the minor differences in diameter on the two sizes of PS2's.

am i missing something? ( other than fairly basic math skills, i mean! )
thanks for any clarification you or anyone might provide.

This kind of thing drives me nuts also and I figured it out a while back but forgot the formula. Bottom line I walked away with was that the heights of tires or Diameters either needed to be exactly the same or if one tire was a tad taller it was better for it to be the front tire not the rear. Based on your numbers it looks like the rear is taller and that is what I understand the problem to be.

right on both counts. 4/10th's of an inch driving me nuts, and taller rears. a guy on another thread has run some oem approved bridgestone numbers and with my current setup im actually a few LESS revs per mile differntial than an OEM bridgestone stock fitment.

so, i'm gonna find something else to obsess about and with our cars that's easy. but i AM sure gonna ditch the old fronts sooner rather than later :rolleyes:

Ok ill get sensors looked at and cleaned 1st ! have a new MAF on order so we will see how it goes.

On a separate note the car all of a sudden wont now boost past 0.5 bar...