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Inspection Procedure 5: Keyless entry system does not work: Notes
WARNING: This page is about a different car, the 2008 Mitsubishi Lancer. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION:
Before replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.