PSM light intermittent flashing, engine power drops

[vrichmd]

I have a 2003 TT and recently the PSM traction control light will flash briefly (maybe 3-5 seconds) and the engine drops power, no other indicators, no check engine light, nothing....light stops flashing and engine power comes back.  If i turn the PSM off, i have no problems, but with ~4,000 rpm shift points in auto and Borla exhausts, the neighbors are getting tired of me.  I was by my mechanic's shop the other day on an unrelated issue and he hooked up the Porsche computer and there were no stored faults in the PSM Management.

 

Anyone seen this? Any ideas?

 

[mihaipopa]

I have had the exact same symptoms, especially on curvy, slopey roads. It would occur both when cruising or under acceleration, in the wet or dry, no matter; the psm light would flash for a couple seconds and there would be a noticeable loss of power, as if the car had no grip.

Problem solved last week with a new set of tires; at least that's what I think. (Only other thing replaced was the coolant reservoir that had developed a leak, about 30k miles after the coolant pipes job, but I don't see how that would light up the psm).

Hope this helps and good luck!

04S, 98k mi

[vrichmd]

Thanks for the reply.  Not sure what it is.  I replaced cooling line a few years ago and the tank last year.  If i get it figured, I'll let you know

[mihaipopa]

no problem. A bit more on my issue: it first started flickering after I had an used michelin installed on the rear ( blowout on the highway, middle of nowhere in Florida, it was the only option at the time). After a tire rotation, with the non-matching michelin now on the front, the psm flickering/loss of power went away.

A few months later, it started again, more frequently, almost daily; did another tire rotation, but no fix. However all the tires were shot at this point.

so, I would check the tires, maybe start with the rears.

[deilenberger]

The PSM is detecting slippage or illogical rotation differences between the wheels and decreasing power in an attempt to keep you going down the road. Your tires are likely way past toast..  this doesn't cause the PSM to store any faults since it's behaving just like it should.

[hahnmgh63]

As mentioned above, a different tire diameter can have an effect. Do you replace your tires in pairs. If one has been replaced after the others have worn quite a lot you almost need to take it in and get it shaved or just replace the other three at the same time. Kind of expensive but it can solve problems. Not sure about Porsche but Audi say's max of 3/16" tread depth difference on the same brand and model of tire as different brands/models can already be slightly different than a standard size. If you have time, you can also remove all of your Brake anti-lock sensors and clean them as they can pick up a lot of debri/dirt and give erroneous readings after a lot of miles, they are magnetic which exacerbates the problem.

[vrichmd]

Thanks for the info.  They're all the same size, 275/40R20 and all have pretty new tread, but I had to replace the front pair after a cut and tires matching the rears were discontinued.

[gh0stman]

Has anyone figured out the root cause of this failure?

[Abe]

hi everyone, Has anyone figured this out?? this is the sec. time that I had this thing happening.  the traction control flashes and engine power drops while cruising or speeding up on the highway??!!

 

thanks for any help

[lewisweller]

Wheel speed sensor fault, dirty rotor pickup ring or indeed a tyre circumference or mismatch tread problem which is more unlikely. Not much else it can be unless some wiring issue between one of the speed sensors and the control module.

[vrichmd]

I believe mine was definitely the tire circumference mismatch.  Doesn't have to be very much of a difference.  I rotated them once they were worn pretty evenly and haven't had the problem since...knock wood