ECM DTC EO47: ECM-BCM Data Problem: Description

The ECM and BCM share information through the UART (Universal Asynchronous Receiver Transmitter) data link. The BCM is the "Master" of the link and data is only transmitted at the BCM's request. Data is sent in eight character "Words" at the rate of 8192 characters per second.

The data from the ECM to the BCM contains engine operating information. The ECM-BCM data includes Coolant Temperature Sensor, RPM and Injector Pulse width values so the BCM can control cooling fans, display RPM and calculate MPG for display at the driver information center. The BCM sends the ECM air conditioning status to be used for idle speed control and ambient (outside) temperature for use in VCC apply and release decisions. Code EO47 is logged in the ECM in the event of a UART fault.

If the fault is a current failure, the ECM will not be able to communicate with the BCM and Code B334 will be displayed as current. (Code EO47 is current in the ECM but can't be sent to the BCM because of the UART fault.) If the UART fault is corrected, both Code EO47 and Code B334 will be displayed as history codes. Code EO47 should be diagnosed using the chart for BCM Code B334 in BODY COMPUTER MODULE article in COMMUNICATIONS DEVICES.