Car stalls using brake pedal

Noticed something unusual last night car stalls if I step on the brake pedal. Also noticed when I turn the key switch to the 1st ON position (car not running) that the idiot lights/warning come ON but when I relax on the key the lights go out and seems to not stay in the on or run position keeping the lights ON. Maybe I have a ignition switch problem? The ignition switch is not but a maybe 2 years old with little use. I was going to order brake switch since it was stalling using the brake but now have second thoughts??? I also have scanner error codes rgt rear speed sensor inopt or reading open however my ABS and PCM lights come on/off but stay on most of the time now but not sure if this is a brake switch, speed sensor or ignition switch problem? Any feedback welcome.

Quotes source post: 7016812

I would never intentionally turn the key to the start position with the engine running. For a possible ignition switch problem, I watched a tech check out my car's ignition switch by starting the engine many times (nearly 10 times maybe even more than 10 times) in rapid sucession. At the same time he was wiggling the key, pressing the key up, in or down, to see if any extra pressure on the key would result in a failure of engine start. The engine started right up every time. But I had experienced times when I turned the key to the start position the engine would not crank. The car's behavior up to that point was the same as it always has been. So, I went ahead and asked the ignition switch be replaced. The complete switch, the mechanical portion, the large alum. casting that holds the steering wheel lock and the electrical switch on the back and the key tumbler assembly at the front and the electrical switch. The key tumbler assembly was swapped from the old lock assembly to the new one. Afterwards the mechanic told me the old assembly looked pretty good and he wasn't sure it would solve the starting problem. I told him I understood but given the car's mileage (220K+ miles) I was prepared to absorb the cost of an unnecessary ignition switch in order to at least eliminate one possible cause of the car's failure to start. Since this switch replacement the car has never failed to start at any time so the assumption is that even though the old part(s) didn't look too bad something in there was bad and causing the no start symptom. My point is that if you are experiencing odd behavior at the ignition -- ignoring the behavior you report when you attempt to turn the key to the start position with the engine already running and I'm not about to test this behavior on my car for you -- an ignition switch assembly replacement appears to be the likely solution. I had to replace a brake light switch -- and clutch switches too -- in my car (oh, an 02 Boxster with 225K miles). The brake light switch replaced cause I noticed that when I stepped on the brakes the lights would not always come on, or would come on briefly then go off. Not safe. The clutch interlock switch replaced in hopes it would cure the no start problem. It did not. At the same time I had the clutch cruise control switch replaced. Both switches cost just a few dollars and the labor was part of the switch replacement job I had the tech do, which I covered above. Sincerely, Macster.

I am inclined to agree with you that the switches are problematic and not a costly DIY.

Quotes source post: 7017236

Just a bit more info: I was told the electrical switching mechanism located at the rear of the casting was a the same as an Audi part and therefore lots cheaper. Picked up one at a nearby Audi parts counter. Counter guy told me I was the second Porsche owner in in to pick up this part. Never had the time to replace the part. Then car failed to start big time. I was just about to call a tow truck when I tried once more and the engine cranked and fired right up as if nothing wrong. Next day early I was at dealer to have the cause diagnosed. Tech tested ignition switch as I described in a previous post. We talked and I mentioned the Audi part I had. He said Porsche stopped selling that portion separately cause too many repairs where just the electrical portion was replaced were coming back. He told me Porsche only sells the complete assembly. The only portion of the old switch that can be swapped over to the new switch is the key tumbler module. I went ahead and had the complete assembly replaced. Just so you know. Sincerely, Macster.

That sounds pricey, you can still get the switch itself from autohausaz and think it is audi part: http://www.autohausaz.com/search/pro...mber=4A0905849

UPDATE: Replaced ignition switch and problem has not recurred.