Engine Light came ON occasionally

My Toyota Camry 1996 model, engine light came on occasionally. I sent it to the workshop for a scan, however, the scanner end with a comm error message after about 20 seconds. He believe his multiscan software may be of different release version or may need to be updated. However, he told me from the engine light flashing, he is able to tell the fault. The engine light flash once then pause then twice then pause. It repeats. According to him, this flash code indicates that the knock sensor is faulty. Appreciate if you can verify this before I replace the knock sensor which is pretty costly and would you be able to tell me where is the location of the knock sensor incase I wish to do the replacement myself. Thanks.