CAN-Bus Terminal Resistance, Powertrain, Checking

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 automatic transmission, ensure the selector lever position is in "P".
Vehicles with manual transmission, ensure the shifter lever position is in "N" with the parking brake applied.
Observe all safety precautions: SAFETY PRECAUTIONS .
View clean working conditions: CLEAN WORKING CONDITIONS .

Test Procedure

Step	Procedure	Result / Action to Take
1	PERFORM: Preliminary Check to verify the customers complaint. Refer to PRELIMINARY CHECK . -- Was Complaint verified?	-- YES: GO TO: Step 2 CAN-BUS TERMINAL RESISTANCE, POWERTRAIN, CHECKING => 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-. IGNITION: OFF. REMOVE: Transmission Control Module -J217-. Refer to appropriate repair information. CHECK: Transmission Control Module -J217- harness connector T52 / 34 to 46 for resistance. SPECIFIED VALUE: 60 - 72 Ω (@ 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, POWERTRAIN, CHECKING => 4 . -- NO: GO TO: Step 3 CAN-BUS TERMINAL RESISTANCE, POWERTRAIN, CHECKING => 3 .
3	REMOVE: Engine Control Module - J623-. Refer to appropriate repair information. CHECK: CAN bus circuit between the Transmission Control Module -J217- harness connector T52 / 34 and the Engine Control Module -J623- harness connector T94 / 67 for resistance. CHECK: CAN bus circuit between the Transmission Control Module -J217- harness connector T52 / 46 and the Engine Control Module -J623- harness connector T94 / 68 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, POWERTRAIN, CHECKING => 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 CAN-BUS TERMINAL RESISTANCE, POWERTRAIN, CHECKING => 4 .
4	Final Procedure Perform a road test to verify repair. -- Does the original DTC return?	-- YES: CHECK: Transmission Control Module -J217- harness connector for any damaged, pushed-out pins. REPAIR: As necessary. If all electrical connections are OK: REPLACE: Transmission Control Module -J217-. Refer to appropriate repair information. Clear the DTC's. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY . Repair is complete. Generate Readiness Code. Refer to READINESS CODE . 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.