E047

TEST CONDITIONS
1. Code EO12 not set;
2. ignition on;
3. Engine speed equal to or greater than 500 RPM for 20 seconds.

FAILURE CONDITIONS
ECM receives bad data from BCM for 3 seconds.

ACTION TAKEN
1. ECM turns on "Engine Control System Fault" telltale;
2. ECM commands BCM to display "Service Soon" message on Driver Information Center (DIC);
3. ECM clears all BCM data from ECM memory;
4. ECM assumes A/C clutch is on at all times for ISC control.

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 Viscous Converter Clutch (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 BCM Diagnostic Charts. B Code Charts

ECM CODE EO47 ECM-BCM DATA PROBLEM

^ Code EO47 can only be displayed as an intermittent. If the fault is present, Code B334 will be current and ECM data cannot be displayed; diagnose using Code B334 chart.

^ The following failures will result in a Code EO47 stored as history
- Both CKT 800D and 800F from ECM to BCM open. Symptoms will be:
A. "SYSTEM FAULT" message on Computer Control Driver Information Center (CCDIC).
B. "ENGINE CONTROL SYSTEM" and "CHECK INFO CENTER" Telltales on.
C. entering diagnostics "NO ECM DATA" Displayed on CCDIC.
D. When fault is repaired. EO47 and B334 will be history.

- CKT 800D or 800F grounded. Symptoms will be:
A. "SYSTEM FAULT" message on CCDIC.
B. "ENGINE CONTROL SYSTEM" Telltale on.
C. Instrument panel gages will flash.
D. Climate control goes blank.
E. Engine cooling fans go high.
F. Diagnostics cannot be entered - CCDIC stays at "SYSTEM FAULT".
G. When fault is repaired. Will show EO47, B334, B335, B336, AND B337 History.

WHEN ALL DIAGNOSIS AND REPAIRS ARE COMPLETED. CLEAR CODES AND VERIFY OPERATION