General Information

4WD Control

U0121 Lost Communication With Anti-Lock Brake System (ABS) Control Module - General Information

Component Location





General Description

CAN communication is a parallel circuit to interchange information among each units. CAN communication can share much information with units more faster and more efficiently by using specified language.
CAN-High line is twisted with CAN-Low line as a purpose in preventing from a noise.
ITM-ECU performs active control by sharing signals of engine RPM, APS, shift position, torque reduction.

DTC Description

This code related to communication line between ECU (ABS) and 4WD ECM (= TCCU : Transfer Case Control Unit) is set when CAN signal from ECU can't received for more than 1 sec or ECU internal error occur.
If failure is detected ITM-ECU prohibits the ITM control and cuts the current to control coil.

DTC Detecting Condition





Diagnostic Circuit Diagram










Signal Waveform & Data




Fig.1) CAN Signal : high & low