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Function Volkswagen Jetta IV

Diesel Fuel Injection - 1.9L Alh, 2V TDI (A4 Platform) 1 illustration ~226 words

Function

The Engine Control Module (ECM) (item 1 ) communicates with the ABS Control Module (item 2 ) and the Transmission Control Module (TCM) (item 3 ) via a CAN - Bus (item 4 ).

Can-Bus Schematic. Scheme 271

Scheme 271: Can-Bus Schematic
Scheme 271: Can-Bus Schematic

At least two Control Modules capable of CAN - Bus are connected together via two CAN -Bus wires which are twisted together (CAN_High and CAN_Low) and they exchange information (messages). Missing information on the CAN-Bus will be recognized as a DTC by the Engine Control Module (ECM) as well as by other CAN-Bus Control Modules.

Two Control Modules have terminal resistors each of 120 ohms, these resistors make sure that the CAN-Bus can function without a malfunction. These terminal resistors are located in the engine and ABS Control Modules.

  1. Test box VAG 1598/21
  1. Test box VAG 1598/18

Vehicles with automatic transmission, see VEHICLES WITH AUTOMATIC TRANSMISSION .

  1. Remove wiper arms and cowl panel: See REMOVAL & INSTALLATION
  2. Release Engine Control Module (ECM) - J248- connector and remove.
  3. Connect test box VAG 1598/22 (through my 1999) or VAG 1598/31 (from my 2000) to Engine Control Module (ECM) -J248- wiring harness.
  4. Check CAN-Bus wiring with terminal resistor in ABS Control Module
  5. Measure resistance between test box sockets 68 + 75: Specification: 115 to 135 ohms If resistance value is within specified range, see «If resistance is within specification»(ref-213881-S37681787522006011900000)