MD166255 is the engine control module (ECU) used in 1991‑1994 Mitsubishi Eclipse 2.0L vehicles; it is a plug‑and‑play unit that does not require reprogramming. Common failure modes include loss of power to the ECU due to blown fuses or corroded connectors, short circuits on the internal board (often from moisture ingress), and sensor input failures such as erratic MAP, TPS, or crankshaft position signals causing a “no start” condition or persistent check‑engine light. Typical symptoms are intermittent engine misfire, rough idle, or failure to start after a power cycle.

First‑check diagnostics: verify 12 V supply at the ECU connector and confirm fuse integrity; inspect all wiring harness connectors for corrosion or loose pins; perform a visual inspection of the PCB for burn marks or swollen capacitors; and review any stored diagnostic trouble codes (DTCs) using an OBD‑I scanner to pinpoint sensor or module faults.[oss-gpt-20b]