Transmission Control Module (TCM) Can-Bus, Checking

Special tools and workshop equipment required 

• Multimeter.
• Wiring diagram.

Test requirement 

• A CAN-Bus malfunction was recognized.
• The Transmission Control Module (TCM) -J217- fuses OK.
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.
• Vehicles with automatic transmission, shift selector lever into position "P" or "N".
• A/C switched off.
• Ground connections between engine/transmission/chassis OK.
• Ignition switched OFF.

Function 

The Engine Control Module (ECM) -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 (ECM) -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 (ECM) -J623-.

Terminal Resistance checking

-- Disconnect the Transmission Control Module (TCM) -J217- T52 electrical connector.

-- Using a multimeter, measure the resistance between the CAN bus low and CAN bus high terminals at the Transmission Control Module (TCM) -J217- harness connector (with ALL other modules connected). Refer to Wiring Diagrams for Pin locations.

Transmission Control Module (TCM) -J217- electrical harness T52 connector terminals	CAN Bus I.D.
34	CAN Low
46	CAN High

Specified value: 50 to 69 Ω (at approx. 20° C)

If the specified value was OK and the TCM is Not communicating:

-- Check the power and ground supply to the TCM module BEFORE replacing a module. Refer to Wiring Diagrams for power and ground inputs. Loss of a power or ground will cause a no response condition from the TCM module. If power and grounds are present at the TCM module, replace the Transmission Control Module (TCM) -J217-. Refer to the Repair information for removal and installation procedures.

If the specified value was Not OK :

Checking wiring 

-- Remove the Data Bus On Board Diagnostic Interface -J533- T20 electrical connector. Refer to the service information for removal and installation procedures.

-- Using a multimeter, measure the resistance of the CAN bus low circuit, then the CAN bus high circuit, between the ECM electrical connector and the ABS electrical connector. Refer to Wiring Diagrams for location.

Transmission Control Module (TCM) -J217- electrical harness T52 connector terminals:	Data Bus On Board Diagnostic Interface -J533- electrical harness connector T20 terminals:
24	6
22	16

Specified value: 1.5 Ω Max.

If the specification was Not obtained:

-- Check the wires for a short circuit to each other, a short to battery voltage, and a short to ground.

-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

-- Repair as necessary.

If the Terminal Resistance was Not OK and no malfunction was found in the wiring:

-- Replace the Data Bus On Board Diagnostic Interface -J533-. Refer to the service information for removal and installation procedures.

If the specified value was Not obtained:

Final procedures 

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .