Can-Bus Terminal Resistance, Selector Lever To Engine Control Module, Checking

Special tools and workshop equipment required 

• Multimeter.
• Wiring diagram.

Test requirement 

• A CAN-Bus malfunction was recognized.
• The Engine Control Module (ECM) - J623- fuses OK.
• The Selector Lever Module -J587- fuses OK.
  Fig 1: Identifying Fuses On E-Box In Engine Compartment, Left Side

  Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.
• 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 the Selector Lever Module -J587-.

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-.

Test procedure 

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK 

Start diagnosis 

-- Remove the selector mechanism, far enough to gain access to the Selector Lever Module -J587- electrical harness connector -A-. Refer to the Repair Information.

-- Disconnect the Selector Lever Module -J587- electrical harness connector -A-.