Data Link Connector (DLC) Wiring, Checking

Relay Panel:

- DLC (terminals -1- and -2-) and terminals -K- and -L- are located in relay panel 1 (in left side of plenum)
- For electrical checking, use multimeter Fluke 83 (or equivalent), VW1594 connector test kit, VAG1598 test box and VAG1598/11 adapter cable
- Switch ignition off before testing wire connections.
- Check wiring and connections for open or short circuits to positive (B+) or Ground (GND), using digital multimeter Fluke 83 (or equivalent) and wiring diagram. Repair as necessary.

Black DLC:
- Ground (GND) and battery positive voltage (B+) to VAG1551
- Terminal -1-: Ground (GND)
- Terminal -2-: B+ supply (from fuse 21, terminal 30)

White DLC:
- Data transfer to VAG1551
- Terminal -1-: not used for heater and A/C diagnosis
- Terminal -2-: data wire for "Rapid data transfer"

Harness Connectors:

The "Rapid 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). 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-.

- Check DLC wiring for open/short circuits to positive (B+) or GND according to wiring diagram, and repair as necessary.

To check wiring to the white DLC, Terminal -2-:
- Remove A/C control head -E87-, refer to "A/C Control Head E87, Removal and Installation". Service and Repair
- Connect VAG1598 test box to A/C control head wiring harness using VAG1598/11 adapter cable.
- Set Fluke 83 multimeter (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, and repair as necessary.

Checking DLC wiring when VAG1551 displays "Error in communication link":

Relay Panel:

- 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 1), 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 or short circuits according to wiring diagram, and 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 clutch control module -J153- or to the A/C control head -E87- was also disconnected at some point.