Ensure PROM is correctly inserted in PCM socket. If okay, replace PROM, clear memory and recheck. If Code P1623 reappears, replace PCM.
Note. To prevent possible electrostatic discharge damage to PCM or PROM, DO NOT touch component leads. DO NOT remove integrated circuit from carrier.
Circuit Description
When ignition is on, theft deterrent module reads key resistor pellet. If proper resistance is recognized by theft deterrent module, it sends a PWM fuel enable signal to PCM. PCM looks for this signal during crank and allows fuel delivery by enabling injectors when signal is recognized.