Data Link Connector (DLC) Wiring, Checking

- DLC (terminals -1- and -2-) and terminals -K- and -L- are located in auxiliary relay panel I (in left side of plenum)



- For wire colors and additional vehicle systems connected to white DLC, See wiring diagram.
- For electrical checking, use multimeter (Fluke 83 or equivalent), VW 1594 connector test kit, VAG 1598 test box and VAG 1598/11 adapter cable.
- Switch ignition OFF before testing wire connections.
- Check wiring and connections for open/short circuits to positive (B+) or Ground (GND), using digital multimeter (Fluke 83 or equivalent) and wiring diagram. Repair as necessary.

Black DLC - battery positive voltage supply (B+)
- Terminal -1- = Ground (GND)
- Terminal -2- = B+ supply (from fuse 19, terminal 30)

White DLC - data transfer
- Terminal -1- = not used for heater and A/C diagnosis
- Terminal -2- = data wire for "Rapid data transfer"

- The "data transfer" wire connection (white DLC, terminal 2) is routed via the K terminal to the A/C control head -E87- connector A, terminal 1 (automatic climate control) and to the A/C clutch control module -J153- terminal D (manual A/C).





NOTE: Other vehicle systems having "Rapid data transfer" On Board Diagnostic (OBD),(for example, multiport fuel injection, automatic transmission, etc.) are also connected to the white DLC, terminal 2 via terminal K.


To check wiring to the white DLC, terminal 2 (automatic climate control):
- Remove A/C control head -E87-.
- Connect VAG 1598 test box to A/C control head wiring harness using VAG 1598/11 adapter cable.
- Set multimeter (Fluke 83 or equivalent) to measure resistance (ohm range) and connect between test box socket 41 and white DLC, terminal 2.
- Reading must be 0 ohms (continuity)
- If not, check wiring for open circuit according to wiring diagram, repair as necessary.

Checking Data Link Connector (DLC) wiring when VAG 1551 displays "Error in communication link"
Check wiring of other vehicle systems having "Rapid data transfer" (for example, fuel injection system, automatic transmission, etc.) in sequence.
- Disconnect other systems from white DLC, terminal -2- at terminal -K- (in auxiliary relay panel I), one at a time.





After each time the wire connection to a vehicle system has been disconnected:
- Re-enter -0- and -8- "AC/Heating Electronics" address word 08 in "Rapid data transfer" operating mode 1.

If control module identification and coding are now displayed:
- Check wiring to last control module disconnected for open/short circuits according to wiring diagram, repair as necessary.

If wiring checks OK:
- Replace control module last disconnected and reconnect all wire connections.


NOTE: If "Control module does not answer" is displayed, the wire connection to the A/C control head -E87- was also disconnected at some point.