[Supras] Two knock sensors or one?

[Bill]

Hi to all,

We're trying to get my son's 1990 Supra to pass state emissions. It has a code 52 for knock and (I am assuming) high HC levels due to spark retard.  This is a non-turbo car. There is some debate as to whether there is a second knock sensor behind the starter. I can't even see a wire going that way, never mind a sensor. I really don't want to take the starter off, only to find there is none! Any suggestions? Thanks for your help!

Bill