will not start on 2002 Ford E-350

when I turn the key there is a click sound

Asked by for the 2002 Ford E-350
2 answers
It's the PCM & TCM . Just had the exact same issue. Problem solved with junk yard parts $90. Dealer wanted $1100 to fix with new parts.

Powertrain Control Module (PCM)
Transmission Control Module (TCM)
2002 Ford E-350, 5.4L V8; 88k miles

Turner-Security.com
Could be a dirty battery cable or a dead battery, try jump starting and if that works its a dead battery, If the battery is good maybe the starter failed.