. Its electrical system and wiring vary significantly depending on whether the engine is a Mechanical Unit Injection (MUI) model or an Electronic Unit Injection (EUI/PEEC) 1. Core Wiring System Components The 3412 engine wiring typically connects the central Electronic Control Module (ECM) to various sensors and actuators.
The 3412 cranks but will not start.
Caterpillar uses a standardized color code. Memorize these from the 3412 diagram: caterpillar 3412 wiring diagram