Do the slow down thermocouples at the cats effect ignition timing in any way? I thought the ignition advance is changed by the Multiplex when the the engine reaches normal operating temperature, but as far as I can tell that is only determined by the temperature sensor at the coolant reservoir. I believe that the temp sensors under the plenum and at the hose neck operate the temperature guage and the cold start system. And the thermocouples only operate the warning lights, but do not effect ignition advance or anything else. But I do believe that they thermocouple signal feeds through the multiplexes, and that is what determines if the slow down lamps are off, flashing, or steady on. So does the signal also effect the timing? But what do I know. Let's hear from the experts out there!
(Assuming that you are talking about a 1981 308i-2V,) No, there's no electrical connection at all between the thermocouples/warning light system and the DigiPlex ignition ECUs. As you noted, the water thermoswitch in the coolant tank is what "tells" the DigiPlexes which ignition map to use.
That's what I thought. Just wanted to be sure I understood. I have an aftermarket exhaust and the thermocouples probes are disconnected. I wanted to make sure that could not effect the ignition or other engine functions in any way.
