E047

DFI Data Circuit:

DESCRIPTION:

The ECM and BCM share information through the UART 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 the Power Steering Pressure Switch, Park/Neutral Switch and 4th Gear Switch status as well as an engine running and Coolant Temperature Sensor status. The ECM-BCM data also includes Coolant Temperature Sensor, Engine Speed and injector pulse width values, so the BCM can control cooling fans, display engine speed 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 E047 is logged in the ECM in the event of a UART fault. If the fault is a hard failure, the ECM will not be able to communicate with the BCM and code B334 will be displayed as current. Code E047 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 E047 and code B334 will be displayed as history codes.

TEST CONDITIONS:

1. Code EO18 clear.
2. NOT cranking.
3. Engine speed greater than 25 RPM.

FAILURE CONDITIONS:

ECM receives bad data or no data from the BCM for 2.1 seconds.

ACTION TAKEN:

1. ECM clears all BCM data from ECM memory.
2. ECM assumes that A/C clutch is on at all times and controls ISC operation accordingly.
3. ECM turns on "SERVICE ENGINE SOON" telltale.
4. ECM tries to send "SERVICE SOON" message to the BCM over the Universal Asynchronus Receiver Transmitter (UART) link.

NOTE ON INTERMITTENTS:

Code E047 should be diagnosed using the chart for BCM code B334.

Code E047 can only be displayed as an intermittent. If the fault is present, code B334 will be current, diagnose using code B334.

Three failures will result in code E047:

1. Open CKT 800/800H between ECM C9 and the UART link.

Symptoms will be:

a. "SYSTEM PROBLEM" message on CCDIC.
b. "ENGINE CONTROL SYSTEM" (ECS) and "CHECK INFO CENTER" lights on.
c. Diagnostics entered "NO ECM DATA" is displayed on CCDIC.
d. When repaired, it will E047 history and B334 current, until key is cycled to off.

2. Grounded CKT 800/800H from ECM C9 to UART.

Symptoms will be:

a. "SYSTEM PROBLEM" message on CCDIC.
b. "ENGINE CONTROL SYSTEM" light is on.
c. At the cluster, speedo is blank.
d. Climate control goes to 75°F and defrost, cooling fans go to high.
e. Diagnostics disabled-CCDIC stays at "SYSTEM PROBLEM".
f. When repaired, it will show E047, B334, B335, B336, B337 history codes.

3. Open ECM CALPAK. (The CALPAK contains communications instructions for the ECM).

a. Symptoms are same as grounded CKT 800/800H.

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