Can-Bus, Checking Terminal Resistance

Function

Control module for Diesel-Direct fuel injection system communicates with other CAN-Bus capable control modules.

These databus-capable components 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. This central terminal resistor is located in the Engine Control Module (ECM).

Special tools and workshop equipment required

Multimeter VAG1526 or Multimeter VAG1715
Connector test kit VAG1594
Wiring diagram

Test Prerequisite

Ignition is switched off.

Test Sequence

-- Remove cover -D- for plenum chamber, right side.

Fig 1: Identifying Covers In Engine Compartment For Plenum Chamber

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Disengage and disconnect connector -A- of the corresponding Engine Control Module (ECM):

Fig 2: Identifying Connector, Engine Control Modules (ECM), And Ground (GND) Connection For Wiring Harness

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

Cylinder bank 1: Engine Control Module (ECM) -J623- (-1-).
Cylinder bank 2: Engine Control Module 2 -J624- (-2-).

NOTE:

Cylinder bank 1 is located in direction of travel, right.

Cylinder bank 2 is located in direction of travel, left.

-- Connect adapter cable (VAG1598/39-2) to test box (VAG1598/42).

-- Connect test box to the corresponding Engine Control Module (ECM). During this, wiring harness to Engine Control Module (ECM) is not connected.

-- Check the central termination resistor at the Engine Control Modules (ECM):

-- To do this, measure resistance between test box sockets 66 +89.

Specified value: 115 to 135 Ω

Resistance Value in Range

-- Connect adapter cable (VAG1598/39-1) to test box (VAG1598/42).

-- Connect test box to the corresponding Engine Control Module (ECM). During this, wiring harness to Engine Control Module (ECM) is not connected.

-- Then, measure resistance between test box

sockets 54 +55.

Specified value: 115 to 135 Ω

Resistance Value not in Range

-- Replace corresponding Engine Control Module (ECM) ENGINE CONTROL MODULES, REPLACING .

Resistance Values in Specified Range

-- Eliminate malfunction in Data-Bus wires or in other Data-Bus components according to wiring diagram: Refer to SYSTEM WIRING DIAGRAM