Permanent 12V battery power used to keep the ECU's internal memory (DTC codes) alive.

Usually defined by multiple connectors (e.g., a 26-pin, 16-pin, 22-pin, and 16-pin layout).

The Toyota 1KZ-TE is one of the most robust and revered 3.0-liter turbocharged diesel engines ever built. Found in legendary platforms like the Hilux, Land Cruiser Prado, Surf, and HiAce, this engine bridges the gap between mechanical reliability and electronic control.

Used for troubleshooting and communication with other vehicle systems.

The absolute most important wire on a 1KZ-TE. The ECU modulates this ground signal to control exactly how much fuel the electronic injection pump delivers. If this wire is broken, the engine will crank but never start.