How to Proceed With Troubleshooting
CAN COMMUNICATION SYSTEM:
HOW TO PROCEED WITH TROUBLESHOOTING
NOTICE:
- DTCs for the CAN communication system are as follows:
U0073, U0100, U0105, U0121, U0122, U0123, U0124, U0126, U0129, C1280, C1296, C1297, and B1499.
- Refer to troubleshooting of each system if DTCs regarding the CAN communication system are not output.
1. INSPECT BATTERY VOLTAGE
Standard voltage:
11 to 14 V
HINT: If the voltage is below 11 V, recharge or replace the battery before proceeding.
NEXT -- Continue to next step.
2. CHECK AND CLEAR DTCs
HINT:
- CAN communication DTCs are output when there is an open or short in any of the communication wires. Any problems with the power source of a corresponding ECU or sensor, or problems in the ECU, the sensor itself also cause these DTCs to be output.
- If a CAN communication wire connector is disconnected with the ignition switch on (IG), the ECUs of the corresponding system and related systems record a DTC.
NEXT -- Continue to next step.
3. CHECK INSTALLED SYSTEMS (ECU AND SENSOR) THAT USE CAN COMMUNICATION
(a) Based on the vehicle equipment and specifications, confirm the systems that use CAN communication Diagnosis System.
NEXT -- Continue to next step.
4. CHECK DLC3 BRANCH WIRE AND CAN NO. 1 BUS CIRCUIT MAIN WIRE (CANH - CANL)
NOTICE:
- Turn the ignition switch off before measuring the resistances of the CAN main wire and the CAN branch wire.
- After the ignition switch is turned off, check that the key reminder warning system and light reminder warning system are not in operation.
- Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the ignition switch, any other switches or the doors. If the doors need to be opened in order to check the connectors, open the doors and leave them open.
HINT: Operating the ignition switch, any other switches, or a door triggers related ECU and sensor communication on the CAN. This communication will cause the resistance value to change.
(a) Turn the ignition switch off.
(b) Measure the resistance according to the value(s) in the table below.
Resistance:
B -- GO TO "OPEN IN CAN MAIN WIRE".
C -- GO TO "SHORT IN CAN BUS LINES".
A -- Continue to next step.
5. CHECK FOR SHORT TO GND IN CAN NO. 1 BUS (CANH, CANL - CG)
(a) Turn the ignition switch off.
(b) Measure the resistance according to the value(s) in the table below.
Resistance:
NG -- GO TO "SHORT TO GND IN CAN BUS LINE".
OK -- Continue to next step.
6. CHECK FOR SHORT TO +B IN CAN NO. 1 BUS (CANH, CANL - BAT)
(a) Disconnect the negative battery terminal.
(b) Measure the resistance according to the value(s) in the table below.
Resistance:
NG -- GO TO "SHORT TO +B IN CAN BUS LINE".
OK -- Continue to next step.
7. CHECK FOR INSTALLED SYSTEMS (ECUS & SENSORS) THAT ADOPT CAN COMMUNICATION
(a) Check which of the following is adopted: dynamic radar / laser cruise control and vehicle stability control.
NEXT -- Continue to next step.
8. CHECK TECHSTREAM
(a) Using Techstream, select "CAN Bus Check" from the "System Select".
(b) Observe the screen for approximately 1 minute to check the ECUs and sensors displayed on the screen.
Result:
NOTICE:
- The systems (ECUs, sensors) that adopt CAN communication vary depending on the vehicle and option settings. Check which systems (ECUs, sensors) are installed on the vehicle.
- Non-installed ECUs or sensors are not displayed. Do not mistake them for being in the communication stop mode.
- Techstream display are affected by signals output from other ECUs which have an open circuit in either of their CAN branch wires.
B -- GO TO "COMMUNICATION STOP MODE TABLE".
C -- GO TO "OPEN IN ONE SIDE OF CAN BRANCH LINE".
A -- Continue to next step.
9. DTC COMBINATION TABLE
(a) Confirm trouble according to the combination of output DTCs regarding the CAN communication system Diagnosis System.
HINT:
- Sometimes CAN communication system DTCs are output, but all the ECUs and sensors connected to the CAN communication system are displayed on Techstream. In this case, previous or history DTCs may indicate the cause of the problem.
- ECUs related to a problem in the CAN bus will store DTCs to indicate communication malfunctions. The communication stop mode in the CAN bus can be determined by comparing the combination of DTCs that have been set. Refer to the DTC combination table for the CAN bus.
NEXT -- Continue to next step.
10. CIRCUIT INSPECTION
NEXT -- Continue to next step.
11. IDENTIFICATION OF PROBLEM
NEXT -- Continue to next step.
12. REPAIR OR REPLACE
NEXT -- Continue to next step.
13. CONFIRMATION TEST
NEXT -- END