How to Proceed With Troubleshooting
CAN COMMUNICATION: CAN COMMUNICATION SYSTEM: HOW TO PROCEED WITH TROUBLESHOOTING
NOTICE:
* DTCs for the CAN communication system are as follows:
U0073, U0100, U0122, U0123, U0124, U0126, U0129, B1207, B1499 and B2326.
* Refer to troubleshooting of each system if DTCs regarding the CAN communication system are not output.
* After the ignition switch is turned off, check that the key reminder warning system and light reminder buzzer are not in operation.
HINT
*: Use the Techstream.
1. VEHICLE BROUGHT TO WORKSHOP
NEXT -- Continue to next step.
2. 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.
3. CHECK AND CLEAR DTC*
(a) Using the Techstream, perform the Health Check (all DTCs check).
NOTICE:
* If there is a CAN communication trouble code that indicates that an ECU or sensor has a power malfunction or interior malfunction which is causing a communication stop, the problem may not be in the communication line.
* When CAN communication related connectors are disconnected with the ignition switch ON or ACC, the ECU related to the connector and ECUs of related systems will store a CAN communication DTC.
NEXT -- Continue to next step.
4. 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.
5. CHECK DLC3 BRANCH WIRE AND CAN NO. 1 BUS CIRCUIT MAIN WIRE (CANH - CANL)
NOTICE:
* Turn the ignition switch off before measuring the resistance of the main wire and the branch wire.
* After the ignition switch is turned off, check that the key reminder warning system and light reminder buzzer are not in operation.
* Before measuring the resistance, leave the vehicle for at least 1 minute and do not operate the ignition switch, any switches or doors. If doors need to be opened in order to check connectors, open the doors and leave them open.
HINT
Operating the ignition switch, any switches or any doors triggers related ECU and sensor communication with the CAN, which causes resistance variation.
(a) Disconnect the cable from the negative (-) battery terminal before measuring the resistance of the main wire and the branch wire.
CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.
NOTICE:
When disconnecting the cable, some systems need to be initialized after the cable is reconnected.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance
B -- Go to "Open in CAN Main Wire" Open In CAN Main Wire.
C -- Go to "Short in CAN Bus Lines" Short in CAN Bus Lines.
A -- Continue to next step.
6. CHECK FOR SHORT TO GND IN CAN NO. 1 BUS (CANH, CANL - CG)
(a) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
NG -- Go to "Short to GND in CAN Bus Line" Short to GND in CAN Bus Line.
OK -- Continue to next step.
7. CHECK FOR SHORT TO B+ IN CAN NO. 1 BUS (CANH, CANL - BAT)
(a) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
NG -- Go to "Short to B+ in CAN Bus Line" Short to B+ in CAN Bus Line.
OK -- Continue to next step.
8. CHECK ECUS CONNECTED TO CAN BUS USING TECHSTREAM*
(a) Connect the cable to the negative (-) battery terminal.
NOTICE:
When disconnecting the cable, some systems need to be initialized after the cable is reconnected.
(b) Using Techstream, select "CAN Bus Check" from "System Select".
(c) Observe the screen for approximately 1 minute to check the ECUs and sensors displayed on the screen.
Result
NOTICE:
* The systems (ECUs, sensors) that use 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.
* The Techstream is affected by signals output from ECUs which have an open circuit in either of their CAN branch wires.
B -- Go to "Communication Stop Mode Table" Symptom Related Diagnostic Procedures.
C -- Go to "Open in One Side of CAN Branch Wire" 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 has 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. CLEAR DTC*
(a) Using the Techstream, clear the DTCs.
NEXT -- Continue to next step.
14. CONFIRMATION TEST
NEXT -- END