Not sure if this is the right place to post this but thought I'd give it a shot.
I'm making my own K-swap conversion harness using only 1 relay and I'm 95% done but there is one thing I can't figure out. I'm only using 1 new relay for the A/F sensor and re-using the stock EK PGM-FI Main relay.
I need to understand how E7 (MRLY) (K20 ECU) gets Voltage Backup (VBU) in a 1-relay setup as it requires power for the DTC memory. In the Hondata schematic it says not to force 12v into it and in the Honda Service Manual it shows 0v with IGN On and 12v with IGN Off. I can see how that would work with an additional relay, but there must be another way around this as most commercially available swap harnesses have a 1-relay design.
I've done a bit of researching and have come across one person that has it grounded in his guide and another that doesn't even have it connected. Neither seem correct, can anybody shed some light on this?http://www.k20a.org/forum/showpost.php?p=2305201&postcount=93http://www.k20a.org/upload/K-Seires%20Pnp%20Harness%20DC2%20&%20EG.rtf
One other thing, which probably isn't as crucial is the power supply on the A/F sensor relay (pin#30). Hondata guide suggests not to use unswitched 12v power otherwise the relay will latch on. But even the RSX service manual shows 12v power comes from an unswitched source:
(Batt > Under-Hood fuse 14 OPTION (30a) > Under-Dash fuse 2 +B LAF Heater (20a) > A/F Relay)
My plan was to use Option +B connector in the EK under-dash fusebox > A/F Relay but will re-consider if there's any chance of the relay latching on. Most others I've seen seem to use switched IGN 12v.
>Hondata K20 Swap Wiring - https://www.hondata.com/tech-k20-swap-wiring
K20a ECU Connector E
K20a RSX factory wiring diagram