Serial Communications

This is serial communications as it occurs in the serial communication circuit (cavity G). This can be viewed with an oscilloscope. It can also be viewed as a fluctuating voltage with an AC voltmeter. The MEFI controllers (ECM’s) broadcast engine operating parameters out on the serial communications wire continuously anytime the key is in the run or start positions. The scan tool translates the information back into a form that is usable by the technician.

This oscilloscope trace was taken right at the DLC cavity G. Seeing this at the DLC verifies that the ECM can send information, the serial communications wire is not shorted to ground or shorted to voltage and has continuity back up to the DLC (Data or Diagnostic Link Connector).