Hey everyone, hoping someone here can help me figure this out.

I’ve got a 2010 Mazda 3 (2.0L). The original ECU was water damaged, so I picked up a donor ECU (LF8M-18-881B from a similar model). I’m using Mazda IDS with a VXDIAG VCX Nano interface to try to set it up.

Here’s what I’ve done so far:

Swapped in the donor ECU.

Connected with IDS – originally showed the donor VIN, but after running through programming it no longer shows that.

Ran module initialization and PATS key programming (programmed 2 keys successfully).

Expected the 10-minute security countdown during key programming, but it never appears. IDS just goes straight through.

Module reset reported “complete.”

Programmed the keys again (both accepted according to IDS).

The car cranks but still won’t start. Immobilizer light does not come on at all.

Current DTC: P1260 (theft detected). Occasionally also see U0100/U0401.

So right now:

VIN issue seems cleared, no longer stuck on the donor VIN.

Keys are programmed (at least IDS says they are).

Immobilizer light isn’t showing, just crank/no start.

Questions:

Do I need to force VIN writing again, or is it already handled since the donor VIN isn’t showing anymore?

Is there a specific step in IDS for the 10-minute security countdown that I might be missing?

Could this ECU (LF8M-18-881B) actually be incompatible with the 2.0L even though it connects and lets me run through programming?

At this point, should I be looking for a different ECU or trying another programming sequence?

Any advice or confirmation would really help before I go chasing another ECU.

Thanks!