Diagnostic Communication

PRINCIPLE OF OPERATION, DIAGNOSTICS
ISAT Scan Tool Diagnostics
The Motronic electronic module communicates with the Scan Tool via pin 55. Communication is two-way and accordingly consists of both input and output signals.

The Scan Tool can communicate with the Motronic system when the ignition switch is in the ON position or when the engine is running. At high engine rpm it may be difficult to establish communication with the Motronic control module.

The Motronic control module retains diagnostic trouble codes that have been stored in its memory even if its power supply fails or is disconnected.

The data link connector is located under the right-hand front seat.

NOTE: Model year 1995 and later cars have only one data link connector (green).

Lamp Flash Codes
To comply with legal requirements in the U.S. market (OBD I), it must be possible for emission-related faults to be signalled by means of lamp flash codes on the CHECK ENGINE lamp (MIL).

The connection (L lead) between pin 13 of the control module and pin 2 of the data link connector is utilized to activate lamp flash codes.

A list of available lamp flash codes and the principle of activation will be found at "Lamp Flash Codes" at System Diagnosis/Procedures/Diagnostic Charts. Engine Control Systems

The Scan Tool cannot be used for activating lamp flash codes.

Care must be taken when grounding pin 2 of the data link connector to activate lamp flash codes as the adjacent pins might be live.