Can Bus Terminal Resistance, TCM To ECM, Checking

Function

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

A CAN malfunction was recognized
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. Refer to: SAFETY PRECAUTIONS .
View clean working conditions. Refer to: 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, TCM TO ECM, CHECKING . NO: GATHER more information from customer about the complaint.
2	REMOVE: Transmission Control Module -J217-. Refer to appropriate repair service information. DISCONNECT: Transmission Control Module -J217- harness connector. CHECK: Harness connector for damage, corrosion, loose, or broken terminals. REPAIR: As necessary. -- Do any DTC's return:	YES: GO TO: Step 3 CAN-BUS TERMINAL RESISTANCE, TCM TO ECM, CHECKING . NO: GO TO: Step 5 CAN-BUS TERMINAL RESISTANCE, TCM TO ECM, CHECKING .
3	The Engine Control Module -J623- must remain connected for the following step. The central terminal resistor is located in the Engine Control Module -J623-. CHECK: Transmission Control Module -J217- harness connector T20m / 10 to T20m / 15 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 5 CAN-BUS TERMINAL RESISTANCE, TCM TO ECM, CHECKING . NO: GO TO: Step 4 CAN-BUS TERMINAL RESISTANCE, TCM TO ECM, CHECKING
4	REMOVE: Engine Control Module - J623-. Refer to appropriate repair service information. CHECK: CAN bus circuit between the Transmission Control Module -J217- harness connector T20m / 10 and the Engine Control Module -J623- harness connector T94 / 68 for resistance. CHECK: CAN bus circuit between the Transmission Control Module -J217- harness connector T20m / 15 and the Engine Control Module -J623- harness connector T94 / 67 for resistance. SPECIFIED VALUE: 0.5 Ω (± 0.3 Ω). -- Were Values obtained?	YES: REPLACE: Engine Control Module -J623-. Refer to appropriate repair service information. GO TO: Step 5 CAN-BUS TERMINAL RESISTANCE, TCM TO ECM, CHECKING . NO: 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 5 CAN-BUS TERMINAL RESISTANCE, TCM TO ECM, CHECKING .
5	Final Procedure Perform a road test to verify repair. Do any DTC's return:	YES: Check the DTC memory. Refer to: DIAGNOSTIC MODE 03 - READ DTC MEMORY . Perform the diagnostic procedure for that DTC. NO: Repair is complete. Generate readiness code. Refer to: READINESS CODE . Return vehicle to Customer.