General Information

General Description

Control Area Network (CAN) is used by the different control modules for communication with other modules. High Speed CAN is used by modules such as ECM, TCM and ESP. Low Speed CAN is used for other modules such as body modules. Both the High and Low Speed CAN lines have both a high and low line. The high and low line mirror each other. This can be see when using the lab scope on the signals

DTC Description

Checking CAN communication, under detecting condition, if an CAN communication error between ECM and TCS is detected. ECM sets U0122.

DTC Detecting Condition





Specification





Diagnostic Circuit Diagram





Signal Waveform & Data




Fig 1) Can communication waveform at idle

Monitoring CAN HIGH and LOW simultaneously is important in monitoring CAN communication waveform. When CAN HIGH signal rise to 3.5V and LOW signal drops to 1.5V - voltage difference between HIGH and LOW signal is 2V - at BUS IDLE state (DIGITAL "1") whose reference voltage is 2.5V, "0" is recognized. Besides, comparing HIGH and LOW signal if opposite waveform is detected with the reference voltage of 2.5V, Check if current cam signal transfers correctly.
Continuous "0"signal above 6BIT means the occurence of error in CAN communication. 1BIT is easily distinguished as calculating the time when "SOF" (START OF FRAME) which notifies the start of frame occurs. Check if "0"signal above 6BIT is detected continuously when monitoring CAN communication waveform.