How To Interpret Communication DTCS (DTCS That Start With U)
- If a CAN communication error cannot be reproduced, determine the suspected malfunctioning part using the DTCs stored in ECUs that are connected to the CAN buses by following the procedure below.
HINT:
Communication DTCs (DTCs that start with U) indicate a communication error between the ECU that stores the DTC and the ECU that is indicated by the DTC.
- If multiple ECUs store a communication DTC for a particular ECU, a communication stop of the ECU is suspected.
*a Items to be Checked - - NOTE:- This DTC table is from another model, and is only used here to show an example of DTCs that are output when there is an open in a CAN branch line for the main body ECU. This table does not show DTCs applicable to this vehicle.
- Even though a DTC title may indicate a communication error with a specific ECU, the ECU name used in the DTC name on the Techstream may differ depending on the ECU that stores the DTC. (Regarding output DTCs, refer to step 6 and the DTC chart for each ECU.)
HINT:
As multiple ECUs indicate a communication stop with the main body ECU, the possibility of a communication stop of the main body ECU is high.
- If almost all of the communication DTCs of an ECU are stored, a communication stop of the ECU is suspected.
*a Items to be Checked - - NOTE:This DTC table is from another model, and is only used here to show an example of DTCs that are output when there is an open in a CAN branch line for the main body ECU. This table does not show DTCs applicable to this vehicle.
HINT:
If almost all of the DTCs of the main body ECU are stored, the possibility of a communication stop of the main body ECU is high.
- When a CAN communication error occurs, many DTCs are output. DTCs other than communication error DTCs (such as DTCs that start with C or B) and communication DTCs for the ABS system are important DTCs, however it may be easier to determine the malfunctioning part by examining the overall situation without considering these DTCs.
- If multiple ECUs store a communication DTC for a particular ECU, a communication stop of the ECU is suspected.
- To help determine the part of the sub bus that has a communication error, prioritize the communication stop DTCs stored in the gateway function equipped ECU.
*a Items to be Checked *b ECM *c Gateway Function Equipped ECU *d Location of Malfunction *e V Bus *f Sub Bus NOTE:This DTC table is from another model, and is only used here to show the ECUs connected to both a V bus and a sub bus. It shows DTCs output when there is an open in the main bus lines for the ECM on the sub bus. This table does not show DTCs applicable to this vehicle.
HINT:
- As gateway function equipped ECUs (sub bus monitor ECU) monitor signals from all ECUs that are connected to sub buses, gateway function equipped ECUs can detect ECUs with a communication stop more accurately.
- When there is a communication stop for the gateway function equipped ECU (gateway), communication with ECUs connected to other buses such as the V bus stops. Therefore, communication DTCs for ECUs connected to other buses are also stored.
- When any of the following malfunctions occurs, many DTCs are likely to be output from many ECUs. Because of this, it may be difficult to determine the probable malfunctioning part.
- Short between CAN lines (CANH and CANL)
- Short between a CAN line (CANH or CANL) and ground
- Short between a CAN line (CANH or CANL) and +B
- Open in a CAN branch line (CANH or CANL) of an ECU or sensor
- Open in a CAN main bus line (CANH or CANL) between 2 ECUs that have a terminating resistor