So im currently in the process of converting my spedometer from mechanical (93 300d) to electric and I need a little help. The electric spedo im using is out of a 94 e420 and I have a dakota digital gps speed sender that I am trying to use to get signal. Ive got everything hooked up but the spedo wont work so I want to confirm some things.. Does anyone know if the e420 spedo uses a Sine wave or Square wave signal? Also the Pulses Per Mile or frequency that the unit needs? Im also having trouble finding which plug on the back of the spedo is for the signal in, and where the ground is etc.