Where is the pcm/ecm on a 1994 mercury grand marques i need to remov one and replace

Interior - Firewall - Above driver's left foot - how do you know that you need to replace it - most diagnostics are done by disconnecting the PCM and checking continuity of the component/wiring at the PCM connector.

i found it and took it out i replaced it with the exact year make and model one i got at pull apart and still not starting i don't know what to do i tried to take the pcm to an autozone to have it testes but they know nothing plz help if you can

does it need to be reflashed

96 grand marquis ls how do u replace it with a new one