My now vintage 2002 996.2 Carrera Cabriolet just flashed the PSM and ABS Failure warning. As a practical and immediate result the engine idles roughly and the accelerator won't activate the throttle. Of course the PSM and ABS don't work either. PSM relies on ABS to function, so any break in the electrical switching and signals that comprise the whole will create this warning. There's a lot out there that discusses this as well as many videos to show the How-To, and many people have successfully fixed this issue. Upon further research, the least cost option on the critical path to fix/repair is replacement of the Swith for Brake Pedal (Porsche Part 996-613-113-03). Dealer price was $33.00 + tax and fix time is under 1 hour start to finish. Tools required: #1 Phillips screw driver; flashlight/torch. To begin, push the seat ll the way back and lower it. Pro-tip: Many tackling this fix have complained about the access namely very tight quarters under the dash, and inability to see anything prolonging the effort and increasing the level of frustration. To minimize effort, improve access and to get your 'mittengrabbens' under the dash to remove and replace the brake pedal switch: 1. Unscrew the footwell vent nozzle tab from the side-vent duct using the screwdriver (see pic). 2. Remove the horizontal section of side-vent ducting that spans from the centre-line dash to the side-vent duct. Once you're done that then use your flashlight/torch to see your work area. The switch in in plain sight. Another tip is when you're replacing the switch and putting it into the steel bracket, don't connect the harness - just put the switch in. Push and twist the switch w/o depressing the brake pedal. Connecting the harness after the switch is seated is easiest. Note the switch socket connection orientation and seat the harness carefully. When replacing the vent duct piece you've removed, its very important to seat the door-side side vent end first and then the centre-line end. If you follow these steps, you will replace the switch and have your car ready in 30 min or less. Lastly, when you start your car it may idle roughly and the warning may still flash. Module needs to POST and re-set. So, after successfully replacing the switch, start the car. Let it run on idle for 5 sec. Turn the car off removing the ignition key and let sit for 5 seconds. Start the car again. If the problem was the switch, then your car will run nicely. You can also check the old switch you've removed with a digital multimeter to verify. If not, then go to the next possibility for PSM and ABS Failure, and/or check error codes and/or see your Certified Porsche mechanic.
Good luck!
