2. Reverse Camera
3. Steering Control
5. Front & Back Speakers
6. Power, Illumination, Handbrake Brake etc
my fault not to self study first.. the seller told me only sockets 5 & 6 are necessary. Seller's own panel acc shop cut the wiring of 2 and 3 already. GG my warranty...
to anyone who wants to change their 1.5 AV player remember to get all 4 sockets!