How do I locate a good Tach source?

A tachometer source can be found in many places in a vehicle. The recommended location for a finding a good tachometer source is: The Negative side of the Ignition coil A Fuel Injector control wire On injectors there are typically two wires. One will be a common color at each injector and the other will be a different color or have a different colored stripe at each injector. The non-common color wire is the correct wire to use. Other possible tach sources: The Crankshaft position sensor (Use for Diesel) The Engine control module (ECM) Non-Recommended tach sources: A Data Module Output Behind the dash at the Tach gauge