Can-Bus Terminal Resistance, Checking

Function

The Engine Control Module -J623- communicates with other CAN-Bus capable control modules.

The control modules are connected by two data bus wires which are twisted together (CAN_High and CAN_Low), and exchange information (messages). Missing information on the CAN-bus is recognized as a malfunction by the Engine Control Module -J623- and the other control modules connected to the CAN-bus.

Trouble-free operation of the CAN-Bus requires that it have a terminal resistance. This central terminal resistance is located in the Engine Control Module -J623-.

Special tools and workshop equipment required

Multimeter
Wiring Diagram

Test requirements

Fuses OK.
Battery voltage OK.
Switch OFF all electrical and electronic accessories.
Vehicles with Auto. Transmission, ensure Selector Lever position is in "P".
Vehicles with Man. Transmission, ensure Shifter Lever position is in "N" with Parking Brake applied.
Coolant Temperature: ≥ 80° C.
Observe all safety precautions: .
View clean working conditions: .

Test Procedure

Step	Procedure	Result / Action to Take
1	PERFORM: Preliminary Check to verify the customers complaint. Refer to . -- Was Complaint verified?	-- YES: GO TO Step 2 CAN-BUS TERMINAL RESISTANCE, CHECKING => 2 . -- NO: GATHER more information from customer about the complaint.
2	DISCONNECT: For Jetta, the Data Bus On Board Diagnostic Interface -J533- harness connector. DISCONNECT: For Beetle, the Vehicle Electrical System Control Module -J519-. The Engine Control Module -J623- must remain connected for the following step. CHECK: For Jetta, the Data Bus On Board Diagnostic Interface -J533- harness connector terminals 6 to 16 for resistance. CHECK: For Beetle, the Vehicle Electrical System Control Module -J519- harness connector terminals 18 to 19 for resistance. Specified value: 60 to 72 Ω (at approx. 20° C). -- Was Value obtained?	-- YES: CONDITION: May be intermittent. PERFORM: Visual Inspection of wiring and component. CHECK: Wiring for open, high resistance, short or harness connector for damage, corrosion, loose or broken terminals. REPAIR: Faulty wiring or connector. GO TO Step 4 CAN-BUS TERMINAL RESISTANCE, CHECKING => 4 . -- NO: GO TO Step 3 CAN-BUS TERMINAL RESISTANCE, CHECKING => 3 .
3	REMOVE: Engine Control Module - J623-. Refer to appropriate repair information. CHECK: For Jetta, the faulty Data Bus On Board Diagnostic Interface -J533- harness connector terminal 6 to the Engine Control Module - J623- harness connector T91 / 80 for resistance. CHECK: For Jetta, the faulty Data Bus On Board Diagnostic Interface -J533- harness connector terminal 16 to the Engine Control Module - J623- harness connector T91 / 79 for resistance. CHECK: For Beetle, the faulty Vehicle Electrical System Control Module -J519- harness connector terminal 18 to the Engine Control Module - J623- harness connector T91 / 80 for resistance. CHECK: For Beetle, the faulty Vehicle Electrical System Control Module -J519- harness connector terminal 19 to the Engine Control Module - J623- harness connector T91 / 79 for resistance. SPECIFIED VALUE: 0.5 Ω (± 0.3 Ω). -- Were Values obtained?	-- YES: REPLACE: Engine Control Module -J623-. Refer to appropriate repair information. GO TO Step 4 CAN-BUS TERMINAL RESISTANCE, CHECKING => 4 . -- NO: CHECK: Wiring for open, high resistance, short or harness connector for damage, corrosion, loose or broken terminals. If no malfunction is found in the wiring: REPLACE: For Jetta, the Data Bus On Board Diagnostic Interface -J533-. For Beetle, the Vehicle Electrical System Control Module -J519-. Refer to appropriate repair information. GO TO Step 4 CAN-BUS TERMINAL RESISTANCE, CHECKING => 4 .
4	Final Procedure Perform a road test to verify repair. Do any DTC's return:	-- YES: Check the DTC memory. Refer to . Perform the diagnostic procedure for that DTC. -- NO: Repair is complete. Generate readiness code. Refer to . Return vehicle to Customer.