Rock

Oh good idea sorry i forgot

whalebird

I am reviving this thread in a search for info. I used to have a Porsche factory training book explaining this system. IIRC the signals for the shift light is not simply an RPM or vehicle speed monitor. The signals for the light are calculated in the control unit. It also takes into account the MPG gauge, which acts like a simple vacuum gauge, but it isnt. There are a complex set of calculations occuring in the ECU that enable this system. My question is that my upshift light quite working. It is not the bulb because the bulb burns ever so slightly all the time. Its not noticable during the day, but at night it faintly glows. Also, my MPG gauge is way off-is sweeps back and forth but is at one extreme or another. I understand this is somewhat normal, but at cruising speed, part throttle, it still measure 0 mpg. It pegs at idle, there is no "modulation". In short, I am wondering if this is indicative of a problem and could be used as diagnostic criteria. I have switched control units(I have a spare) and nothing changes at all. The car runs great, but sometimes I get what seems like a rich running condition that occurs at wide open-high rpm situations. I have replaced all sensors(temp,throttle,oxygen, etc.)and fuel press. reg. and dampener, all injectors. The only variable not elimanated is my AFM. It tests ok.
Anyone have any in depth info on this system-I have no idea where my factory training material that went into great detail is.