SELF-DIAGNOSIS
- CAN self-diagnosis is performed by each ECU connected to the CAN bus.
- Diagnostic trouble codes related to communication are named with the capital letter U, and are called "U-codes."
- A summary of the CAN self-diagnosis system is presented below. For further details on each diagnosis code stored by the ECUs, consult the U-Code Diagnostic Trouble Code List
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TIMEOUT
Each ECU transmits data frames periodically. If the intended receiving ECU cannot receive the data frame within the specified period, it sets a diagnosis code indicating communication timeout for the ECU that failed to transmit. A data length is assigned to each data frame. If a data length is shorter or longer than the specified, the ECU cannot receive the data.
BUS OFF
Related to a communication error that persists even after the transmitting ECU attempts recovery for a specified number of attempts or that persists for a specified period after recovery. Communication is stopped and this diagnostic code is issued.
FAILURE DATA
When the transmitting ECU detects failure of a sensor directly connected to it, this is the pertinent data used to inform the ECU.
DYNAMIC RANGE ERROR
When the data received exceeds or is less than the prescribed range, this diagnosis code is issued.