Speedometer And Tachometer
The input information for the speedometer and 
tachometer is supplied over the Class II serial data link by the Powertrain Control Module 
(PCM) for the 4 cylinder engine, and by the Body Control Module 
(BCM) on the V-6 engine. The BCM gets the vehicle speed data from the Engine Control Module 
(ECM) via the CAN serial data link.