Neat project. A few years ago I tried and failed to get a junkyard Toyota security ECU from a ‘96 4Runner to work for remote lock/unlock in my ‘94 Land Cruiser with an eBay key fob. I might revisit it with this approach - cheap and easy RF analysis software/hardware would have eliminated a lot of guess work … though if memory serves I think the real headache was decoding wire colors in the security harness, which were not all explicitly labeled in the manual for “security” reasons.