CEL code after engine replacement

[CuttyVert]

The engine in my wife's 2001 Avalon blew over the summer. I managed to find one from a 2002 with 40K. The engine was installed and runs fine but now throws a code for the O2 sensor. The sensors are OK. If you clear the codes, the CEL will come on almost immediately when you start it back up. My mechanic is pretty good and it has him stumped. I've been looking around at ECU's and noticed that the 2002 has a different part number than the 2000-2001. Does anyone know if this could cause the problem?

[csaxon]

What's the code?

[CuttyVert]

Sorry for the delay. There are two codes showing up.
P1135
P1155

[csaxon]

Unusual for both to malfunction. Check the owners manual for the location of the A/F sensor heater relay. It's usually in the relay/fuse box next to the battery and air filter box. The relay is marked as A/F Heater or A/F HTR. Check for continuity between terminals 1 and 2 and NO continuity between terminals 3 and 5.
To check relay operation apply battery voltage across terminals 1 and 2 and check that there IS continuity between terminals 3 and 5.

[CuttyVert]

The relay checks out fine. The A/F sensors themselves check out and all the wiring passed continuity checks from the computer to the sensors. My mechanic thinks it must be the ECU and has one coming.
Back to my original post about the ECU: Since the Avalon has a smartkey (chip in it), if the computer is changed out will it need to be programed to be compatible with the key?