Transfer System > Transfer Case Assembly > U0001 High Speed CAN Communication Bus off

Component Location

General Description

CAN communication is a parallel circuit to interchange information among each units.

CAN communication can share much information with units more faster and more efficiently by using specified language.

CAN-High line is twisted with CAN-Low line as a purpose in preventing from a noise.

The operating duty of EMC is maintained at 100 : 0 (2WD) for guaranteeing stabilized driving force, accuracy of the control during inside ABS, FTCS, ESP control.

DTC Description

This code related to communication line between ECM(PCM, ABS, ESP) and "4WD-ECM" is set when CAN signal from ECM(PCM, ABS, ESP) can't received for more than 1sec or ECU internal error occur.

If failure is detected "4WD-ECM" prohibits the "ITCC" control and cuts the current to control coil.

DTC Detecting Condition

Item

Detecting Condition

Possible Cause

DTC Strategy

•	CAN Bus Off

•	Connector looseness and poor terminal to wire connection.

•	CAN HIGH/LOW circuit open/short.

•	Faulty CAN MODULE.

•	Faulty 4WD-ECM .

Threshold Value

•	CAN Transmit counter exceeds 255 will reset CAN module. (reset cycle 1 sec)

Fail Safe

•	Change into 2WD mode.

Schematic Diagram

Signal Waveform & DATA

Monitor DTC Status

1.	Connect scantool to Data Link Connector(DLC).

2.	Warm up the engine to normal operating temperature.

3.	Monitor DTC(Diagnostics Trouble Code) on the scantool.

Is the same DTC displayed again?

	▶ Go to " Inspection/Repair " procedure .
	▶ Fault is intermittent caused by poor contact in the sensor’s and/or "4WD-ECM"s connector or was repaired and "4WD-ECM" memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of vehicle Repair" procedure

Terminal And Connector Inspection

1.	Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

2.	Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration,or damage.

Has a problem been found?

	▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure.
	▶ Go to "CAN comm. Line Inspection(Open/Short) " procedure.

Control Circuit Inspection

CAN Comm, Line Inspection(open/short)

1.	Ignition OFF.

2.	4WD ECM : Disconnect.

Measure resistance between CAN(HIGH) terminal of 4WD ECM harness connector and CAN(LOW) terminal of 4WD ECM harness connector.

Specification : Approx. 60Ω

The above value is only for reference.

The actual value may differ from it according to various engine condition.

Is "resistance" display near the specified value?

	▶ Fault is intermittent caused by open or short in CAN signal harnessor was repaired and "4WD-ECM" memory was not cleared. Go to the applicable troubleshooting procedure.
	▶ Check for open or short in TCCU communication circuit. ▶ Check PCM, ABS, ESP or their signal. ▶ Repair or replace as necessary and go to "Verification of vehicle Repair" procedure.

Verification of Vehicle Repair

After a repair, it is essential to verify that the fault has been corrected.

1.	Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode

2.	Using a scantool, Clear DTC.

3.	Operate the vehicle within DTC Enable conditions in General information.

Are you DTCs present?

	▶ Go to the applicable troubleshooting procedure.
	▶ System performing to specification at this time.