As I just stated in another post, the new type knock sensor replacement part is a one piece part with both knock sensors and that's the only way it comes now (for years).

I've seen this problem occur a few times before too and the tech is probably correct, the ECU is probably the cause of the check engine light (knock sensor code).

Most techs start with replacing the knock sensors because it's the most obvious and probably cheapest place to start. The code is always intermittant and takes days-weeks usually before it re-occurs after clearing the code with NO status messages for further assistance either. The cure is then 3 things:

1)knock sensor "kit"

2) ECU

or 3) wiring between ECU and knock sensors (havent seen that yet).

A long shot.....but if you and/or the tech have any doubts, see if they'll let you try another ECU from a used car off the dealers lot just to see if that fixes the problem before commiting yourself to the cost of a new/used ECU.