2001 sequoia check engine light on problem

I purchased a 2001 Sequoia and in few weeks the check engine light came on. I had a mechanic who inspected the vehicle and didn't find any apparent faults, we came to conclude that it was the ECU problem. It's seems confirming by the fact that after we had installed the ECU in another Sequoia vehicle the check light was on. So now I have only solution to replace the ECU, but that would cause another problem with key recognition. How can I make the old master key recognized by the new ECU? Or to put it simply can I re-program or reset the ECU memory to make the engine light disappear? Any recommendation is highly appreciated.

I purchased a 2001 Sequoia and in few weeks the check engine light came on. I had a mechanic who inspected the vehicle and didn't find any apparent faults, we came to conclude that it was the ECU problem. It's seems confirming by the fact that after we had installed the ECU in another Sequoia vehicle the check light was on. So now I have only solution to replace the ECU, but that would cause another problem with key recognition. How can I make the old master key recognized by the new ECU? Or to put it simply can I re-program or reset the ECU memory to make the engine light disappear? Any recommendation is highly appreciated.

In my opinion it having a ecu problem is very unlikely, take it to another mechanic for a second opinion