U2105 - LOST COMMUNICATION WITH ECM

The ECM (Engine Control Module) is the control unit that is responsible for a series of engine actuators to ensure optimum engine performance. The ECM is provided with various readings from sensors that are installed on the vehicle, and it interprets the data using multidimensional performance maps, commonly known as lookup tables and adjusts the actuators accordingly.

The Engine Control Module also controls the fuel system, ignition timing, and idle speed. All of these were previously mechanically controlled. Now, with this controller regulating the performance of these systems, it does so electronically based on the data provided by the actuators and sensors.

The information from the ECM and all the control modules is sent through a communication circuit known as the CAN bus (Control Area Network). It is through this circuit that operating information and various commands necessary to achieve good performance of the car are provided. The modules contain programmed data about the messaging to be interchanged on the network’s serial interface, and some regular messaging is carried out by the receiving module as an indication of the readiness of the transmitting module. If a supervised periodic message is not received from the ECM, which indicates its availability, the DTC U2105 OBDII code will be set.

• Check Engine Lamp on.

The reasons for setting the U2105 OBD2 fault code are:

• The electrical connections to the Engine Control Module could have inconsistencies.
• The power supplied to the ECM may not be correct.

The steps to troubleshoot the U2105 OBDII diagnostic code are as follows:

• Consult the Technical Service Bulletins.
• Check if other DTCs are stored, especially for communication failures of a particular control module.
• Perform a diagnostic on the system circuit. Check for deficiencies due to burned wires or corroded connectors. Repairs or replaces as required.
• Check the performance of the ECM's battery voltage and ignition circuits. If you discover a short or open circuit, make repairs.
• Check that the CAN bus circuit communicating with the module is not open. Repair electrical connections as necessary.
• Inspect the condition of the ECM connectors and cables for damage. Correct it as required.