2zz Swap on Vitz/Yaris SCP90

[CTScott]

Originally Posted by blindmanwatching

There are numurous wiring diagrams available online, for the 2001 celica, but I cant understand the whole concept of how the ECM is wired to the OBD2 plug. Need help with that.

Wiring to the OBD plug is typically very trivial. That vintage is ISO9141, so there is one (K line) wire that is the communications wire.

Pin 16 is constant 12 V power
Pin 4 and 5 are grounds
Pin 7 is SIL, which is a direct connection to the ECM
Pin 13 is TC, which is a direct connection to the ECM

An OBDII reader communicates with the ECM via pin 7, which is the "K Line". For a standard OBD reader, just 4,5,7 and 16 are needed. Pin 13 is a toyota specific diagnostic wire.