Can-Bus Terminal Resistance, Powertrain, Checking

WARNING: This page is about a different car, the 2019 Audi SQ5 and 2018 Audi Q5. However, it is still accessible from the selected car via links, so may be relevant.

General Description

The Engine Control Module -J623- communicates with all databus capable control modules via a CAN databus.

These databus capable control modules are connected via two data bus wires which are twisted together (CAN_High and CAN_Low), and exchange information (messages). Missing information on the databus is recognized as a malfunction and stored.

Trouble-free operation of the CAN-bus requires that it have a terminal resistance. The central terminal resistor 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.
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. -- NO: GATHER more information from customer about the complaint.
2	The Engine Control Module -J623- must remain connected for the following step. The central terminal resistor is located in the Engine Control Module -J623-. REMOVE: DSG Transmission Mechatronic -J743-. Refer to appropriate Service Information. CHECK: DSG Transmission Mechatronic -J743- harness connector T23 / 19 to T23 / 18 for resistance. Specified value: 60 - 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. -- NO: GO TO: Step 3.
3	REMOVE: Engine Control Module - J623-. Refer to appropriate Service Information. CHECK: CAN bus circuit between the DSG Transmission Mechatronic -J743- harness connector T23 / 19 and the Engine Control Module -J623- harness connector T91 / 79 for resistance. CHECK: CAN bus circuit between the DSG Transmission Mechatronic -J743- harness connector T23 / 18 and the Engine Control Module -J623- harness connector T91 / 80 for resistance. SPECIFIED VALUE: 0.5 Ω (± 0.3 Ω). -- Were Values obtained?	-- YES: REPLACE: Engine Control Module -J623-. Refer to appropriate Service Information. GO TO: Step 4. -- NO: 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.
4	Final Procedure Perform a road test to verify repair. -- Does the original DTC return?	-- YES: CHECK: DSG Transmission Mechatronic -J743- harness connector for any damaged, pushed-out pins. REPAIR: As necessary. Clear the DTC's. Refer to Repair is complete. Generate Readiness Code. Refer to . Return vehicle to Customer. If all electrical connections are OK: REPLACE: DSG Transmission Mechatronic -J743-. Refer to appropriate Service Information. Repair is complete. Generate Readiness Code. Refer to . Return vehicle to Customer. -- NO: Perform the diagnostic procedure for any DTC's. If no DTC's return the repair is complete. Return vehicle to customer.