Data Link Connector: Description and Operation

DESCRIPTION

The Data Link Connectors (DLC) serve as the interface between the Engine Control Module (ECM), Transmissiom Control Module (TCM) and the diagnostic equipment used for retrieving fault code information.

There are three main signals conducted by the DLC's
^ Exciter Signal
^ Blink Code Output Signal
^ Diagnostic Signal

The Data Link Connectors are made up of 4 separate connectors with 2 pins each.

1 Black Connector - Power supply
Pin 1 to Ground
Pin 2 to power from fuse 27

2 Black Connector - Rapid data tranfer for Scan Tool
Pin 1 to ECM Terminal 13 & TCM Terminal 15
Pin 2 to ECM Terminal 55 & TCM Terminal 51

3 Brown Connector - Instrument cluster diagnosis
Pin 1 unassigned
Pin 2 to Instrument Cluster

4 Yellow Connector - Blink code output
Pin 1 unassigned
Pin 2 to ECM Terminal 22

VW Special Tool VAG 1551:

The VAG 1551 tester may be used to retrieve Diagnostic Trouble Codes (DTC).

Extracting Diagnostic Trouble Codes Using LED Test Light:

Blink codes may be retrieved with a "LED" test lamp.

EXCITER SIGNAL

Description

The Exciter Signal is connected to pin 13 of the Motronic control module, the signal is directional IN only (PIN 13 - INPUT ONLY).

The exciter signal is used for activation of rapid data download (Diagnostic Trouble code extraction) via the white data link connector (L-wire).

Signal Failure

When there is a break in the signal wiring (L-wire), the following text appears on the V.A.G. 1551: "control unit does not answer".

BLINK CODE OUTPUT SIGNAL

Description

The Blink Code Output Signal is connected to pin 22 of the Motronic control module, the signal is directional OUT only (PIN 22 - OUTPUT ONLY).

This signal is used for blink codes (Diagnostic Trouble Codes). The malfunction indicator lamp (CHECK ENGINE) in the dash panel of vehicles with California emissions is activated by this signal. The blink code output signal is also supplied to one of the data link connectors for LED test light blink code access.

DIAGNOSTIC SIGNAL

Description

The Diagnostic Signal is connected to pin 55 of the Motronic control module, the signal is bidirectional (PIN 55 - INPUT + OUTPUT).

The diagnostic signal is used for communication between the Motronic control module and special tool V.A.G. 1551.

Signal Failure

When there is a break in the signal wiring (K-wire), the following text appears on the V.A.G. 1551: "control unit does not answer".