Knock Sensor Location

Does anyone know where the knock sensors on a '91 C2 are located?

My check engine light recently came on, and after some digging around, I figured out how to get the computer to report its error codes. It seems to think that there is a problem with "knock sensor #2". Unfortunately, I don't have a service manual and haven't been able to spot anything that looks the part in question. Any hints?

Thanks.

Under the shroud but attached to the top of each bank of cylinders is a bridge with the knock sensor attached.

I was afraid that they had hidden those sensors under there. Thanks for the help.