how to read connectors

That's the problem, there's no global standardisation. Amp-Tycho, Molex and Kram in Denmark make most of them but it's Toyota or GM or Mercedes who decide the pin-outs. Even with OBD II, the only standardisation is 12v+, 12v+ ign. and CAN Hi Lo in certain positions. VSS on Mits. and tach especially BMW and Toyota is in the same position but that may be coincidence. We had this years ago with the ISO car audio plugs for Europe. Except it was never standardised, Ford, all the Orientals including European built and BMW never followed it. Worse, whilst Renault and Mercedes followed the pin convention, Ciroen/Peugeot, VW and Opel switched the constant and ACC wires. Peugeot even turned the ACC into a mux data wire! When changing head units, you changed over the red and yellow and fed the red directly to ignition switch or fuse box! If you didn't you guaranteed DTC being thrown or no remote locking! Audi have never used an ACC on their radio looms.