Tony Labarge

Hello i have a 2000 tahoe z71 that has no sound coming from rear door speakers! Im wondering if there’s a factory amplifier somewhere that im not seeing? I checked behind the glove box and nothing.. its a non bose system so im not sure if there is an amp? If there is where is it? I do have a after market head unit but its wired correctly pulled the door speaker and put a multi meter on it and its reading above 5.0 ohms on a 4 ohm speaker does that mean its done? Somebody help lol