DTC P1608 - Engine Control Module (CPU) Malfunction: Condition
WARNING: This page is about a different car, the 1997 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.
DTC is set when Engine Control Module (ECM) does not read DTCs from output devices. Cause is malfunctioning ECM. Replace ECM and erase any DTCs present. See CLEARING CODES under SELF-DIAGNOSTIC SYSTEM. Retest vehicle.