I see these are currently all the rage in the MR2 community. Very readily available, cheap and are 95% identical to a ST215. There are some internal difference (rings, etc) but overall are vastly identical to a Gen4 swap.

The only difference -- is in the electronics. The ST246 utilizes an engine immobilizer within the ECU. No paired keyfob/transponder -- ECU no worky worky and no swap starting.

Couple options I've seen to resolve this involve doing a full standalone ECU, buy a keyfob, transponder, new igintion cylinder (to match keyfob), get dealer to program transponder/keyfob to ECU, and I've seen that TCS is able to remove the transponder from the ST246 ECU (effectively making it a ST215 swap).

I guess the question becomes is this worth it? For sake of ease, I'd probably do the TCS route. Since I'll be sending the harness over to MR220v for conversion, the ECU may as well go out to.

I could always just do a gen4 swap again -- but that's looking in the 1500-1800 price range right now for me to pick one up locally. Online is still in the 1500 range after shipping and damn import fees.

If the cost to swap the ECU out is nominal, may as well do the gen5 swap, pick it up locally for 900 (I've been negotiating with an importer right now saying it's useless without keyfob and transponder due to the immobilizer).

Not like anyone here drives a celica anymore -- but throwing it out here for discussion.