The ECM and engine stop and start ECU assembly communicate with each other via the CAN communication line. The engine stop and start ECU assembly also communicates with other computers through the ECM. If there is a problem in this communication, the ECM illuminates the MIL and sets the DTC.
DTC No.
DTC Detection Condition
Trouble Area
U1103
No communication between ECM and engine stop and start computer (1 trip detection logic)
ECM to engine stop and start computer circuit
ECM
CAN communication system
WIRING DIAGRAM
INSPECTION PROCEDURE
Go to CAN communication system for troubleshooting (Click here).
HINT:
When DTCs indicating a CAN communication system malfunction are output, repair the CAN communication system before repairing each corresponding sensor.
Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
If the CAN communication malfunctions, there is no data output from the ECM. In this case, some of the freeze frame data are not correct and not identical with the ECM data, but the ECM data are correct.
