I swapped out the original 2 channel radio from my Tercel with a factory 4 channel amped unit... went like a dream (nothing like factory parts!) but can't locate the rear speaker leads... Not in trunk, 1/4 panel trim or under rear seat. I'm sure the harness is the same for all Tercels... think they cut them off? Any ideas?
Did u check the underside of the rear deck? Also, when you match up the install harness with the factory plug, and look at the factory harness, does it even have wires for the rear speakers? Finally, I'm assuming since you said it's a 2-channel radio that you meant that the car only came with two speakers (fronts).
I've found almost always that they use the same wiring throughout the car regardless of whether or not a particular option is installed. I've seen many vehicles that had the "no radio" option but that have all 4 sets of speaker wires run to their proper locations, as well as a harness somewhere in the dash that is specifically for a radio. My advice would be to make sure the factory plug does indeed have those rear speaker wires, and assuming it does, just keep on looking in the back of the car til you find them.
Yup, Checked there also... The factory plugs at the amp have all the required wires too. Others with Toyotas have told me wiring was ready and just hanging there waiting for rear speakers, not mine though. :") I'm going to remove more trim and completly remove the rear seat next... I've stripped the darn car nearly to the console so running the wires myself won't be such a task now anyway!