When my girl friend got the car the stereo wiring was a mess so i wired it in how the last owner did

(bye passed the active setup) while i sourced a genuine toyota stereo plug as this had been cut off.

Today ive soldered the original plug back on and connected up the stereo with a iso-toyota lead.

Its really quiet and the quality is crap.

now from a search i found it may be the active setup amp located behind the seat belt area but how can i test if its xxxxx? Also the power on the perminant feed is

.5v while the ignition is the full 13v
Cheers