Crankhome VR trigger see InputTrigger/AudiTrigger (also related: MembersPage/AudiA6C4 )
Checked crankhome-VR with DSO138 scope. It was -peak first, than +peak, which was NOT good, had to be swapped as instructed on VemsAudiAan
- Swapped red and violet wires.
- Checked crankhome-VR again with DSO138 scope
- scope Black probe: GND AAN motronic55/pin48
- scope Red probe: crankhome-VR AAN motronic55/pin47
- now good: +peak first, -peak follows since LM1815 triggers on negative going zero crossing.
The signal is rather noisy, even without ignition on... Remember this is a $20 scout-level 1 channel scope circuit. (out of the box, without even putting it into a plastic or wooden case; which "wood" be nice). The "OK" button froze the screen so a short cranking was enough.
This crankhome-VR signal relates to "Geber fur Zundzeitpunkt":
Which is in the factory install actually -peak first, +peak follows. The diagram shows the good polarity required for VEMS: +peak first, -peak follows.
The AAN engine crankhome-VR wires were good (in this factory harness and VR-sensor) with red in middle (maybe contradicting the VemsAudiAan page but the scope is always right).
Notes:
LSU4.9 sensor was only put in the exhaust after the engine started. Actually started on first start-attempt. (not when scoping, obviously since ECU was not installed).
- There is no point in contaminating the LSU4 sensor in case engine does not start (most often it does NOT start on first attempt, there are usually many things to check, timing-light the engine, and so on...).
- The LSU4 sensor can last 1000+ hours if running on cruise power close to stoich, but fuel, soot or other contamination shortens lifetime significantly.
- Dropping on the floor shortens lifetime extremely quickly.