Brake light problem

[Jesper Hougaard]

My 996 Carrera Cabrio, 2001 C4 (Manual 6 speed, no cruise control) has a peculiar problem: When activating the brake switch (when braking) the engine stalls and dies, but when taking out the switch everything is fine. My Durametric comes up with various codes, such as P1219 (256), P1578 (428), P0121 (117), P1121 (430) and P1122 (431) when it happens, but all disappear once I disconnect the brake switch - but of course, the brake lights won't work without it. And yes, I have tried putting in a new switch - same result, even when jumping the plug without the switch. As part of fault finding I have traced all the wires to the 4 brake lights as well as to the ECU - all are OK with no shorts. Any suggestions?