My original post on this topic disappeared into the ether with the recent server crash..... I'll try again.
We needed both the pinout of the Bosch Motronic 7.3 ECU's and the WSM. [I believe this information is pretty much "public domain" for most cars, but I could write a book on how tough it was getting it for this car....]
1. RPM - Shows up on pin F35 of the "vehicle connector" legend on the ECU diagram. The WSM says the wire on that pin is "black/brown" and that it goes to *lots* of places - The pdf manual is *righteous* at this point as clicking, eg, a connector, opens a window showing the physical thing, its location in the car, and it's pinout - etc....
While "clicking around" we turned up a 4-pin connector, in the correct location [behind the passenger seat] that didn't have a "mate".... At this point we removed the cover in the car - Finding that connector, with wires that agreed with the WSM (!) was a big boost - As a test, we simply "poked" the wire from the Traqdata RPM port into the appropriate pin on the connector, and immediately saw ~520rpm on the DU - Very cool! [ This is, of course, 50% of the real #, but that's easily fixed] Used a suitcase connector to make the connection for real.
2. Accelerator pedal position - Pins F08 and F40 of the vehicle connector -> Chase these thru, and they're both going in to connector 12G behind the passenger seat. Strip back some of the covering on the bundle, and there they are - Suitcase connector again and give it a go - The Traqmate was set at the default 20v full scale, but we still read between 0.75v and 3.75v idle to WOT (ign only....) - Hopefully setting the Traqmate to 5v FSD will render a "nice" TP graph.
[BTW, there are two separate TPS circuits, (pins F08 & F40) and obviously we only tapped into one of 'em - I was a little concerned that there may be a "load" applied by the TM that could throw the two out of sync - Which would be bad as apparently the car then stops - But, "no worries", as someone once said.....]
3. "Brake switch" and "brake light switch" are also available from the ECU. However, there's a relay board in the correct location, and a quick view of that onscreen told us which relay was in the brake light circuit - Test with the ubiquitous "test lamp" and away we go.....
Other "stuff" that we noticed while poking at this thing, and on which comments would be appreciated:
1. "Catalyst temperature" is "available" in the same part of the loom as we attacked for TP. - Is it worth feeding that to an analog input?
2. "CAN line hi", "CAN line lo" and "diagnostic K-line" are "available" all over the place!....... Comments?