Mine comes on randomly. Never at start up. Only when moving.
I don't have the luxury of a porsche reader so here's what I've done already.

1. Cleaned the MAF.
2. Changed air filter.
... still comes on
3. Changed front and rear pads rotors and new brake sensors.
4. Changed all 4 speed sensors (what a job. Over 2 hours of frozen stuck sensors!!!! Had to use a torch and rip these things out. They were really frozen on. Yards of brass pulling out and prying on the little buggers to get them off.



....drove a.little and it didnt come on yet.

Cross fingers! If not im.gonna try:
brake sensor

 

If you are talking about the brake wear sensors they have nothing to do with those lights.

Brake lights work? Need access to a decent code reader.

 

If it only comes on above 78 mph your spoiler brake light is out. Mine had this issue...turns out it had flown out entirely.

 

Shoot. It came on again and the reader I got doesn't say anything with car on. If I shut her down and restart the lights come off.

I was doing about 67 to 70 and it came on. Ok. Time to check all lights and bulbs.

 

I was having this issue a few weeks ago, I replaced the brake pedal switch and that fixed it https://www.pelicanparts.com/cgi-bin...og_description

 

^^^ +1 on checking the brake switch.

 

Yep! Got a hold of a reader at a local garage...

Error 4340! Brake switch.

Damn bugger. Ordered!

 

Paraphrasing from Page 209 of the essential companion with regards to MAF sensor:
IF the MAF sensor warning is triggered, that has a downstream effect, specifically psm and abs will fail.

I have both psm and abs lights and a new MAF but I haven't tested it yet. It's on my list...

 

Woo hoo! Fixed! I drove about 200 miles today.
Got a new brake sensor. That little bugger was hard to put in!! No ABS/PSM errors!!

986

While playing with it I swapped out 6428 license bulbs with LED. haha!