ECM Back-Up Power Source Circuit

Battery positive voltage is supplied to BATT terminal of ECM even when ignition switch is turned off for use by the diagnostic trouble code memory, air/fuel ratio adaptive control value memory, etc.

Fig 1: ECM Back-Up Power Source Circuit - Schematic

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Fig 2: ECM Back-Up Power Source Circuit - Diagnostic Flowchart

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002