On Board Diagnostic System

Diagnostic Socket Description:

GENERAL DESCRIPTION
The Motronic 1.8 ECU has on-board diagnostic capabilities which are accessed through the diagnostic socket. The diagnostic socket has three diagnostic control functions as explained below.

CONTROL FUNCTION #1 (fault codes):
The on-board diagnostic system carries out continuous system checks and monitors several components during engine operation. If the ECU detects a problem in a system or component, it stores a fault code in memory.

The fuel ECU can identify and store 18 fault codes.

When the engine is stopped, fault codes can be extracted from the ECU via the diagnostic socket.

CONTROL FUNCTION #2 (input device test):
Control function #2 aids the technician in checking the operation of selected ECU input devices. An acknowledgement code tells the technician if the input device is operating.

CONTROL FUNCTION #3 (output device test):
Control function #3 aids the technician in checking the operation of selected ECU output devices. By placing your hand on the component or listening for component operation, you can verify if the output device is operating.

Code Example:

DIAGNOSTIC SOCKET OPERATION:
The diagnostic socket has a button, a light diode and a selector cable. When carrying out fault tracing, the selector cable must be placed in its appropriate socket.

IMPORTANT: For Motronic 1.8 troubleshooting use socket 2 (of the 6 available).

Codes stored in memory are displayed as a series of flashes from the light diode in the diagnostic socket. All codes have three numbers, each ranging from 1-9. The code can be read by the number of flashes delivered by the diode.

Since all codes have three numbers, each code requires three series of uninterrupted flashes. There is a three second interval between the series of flashes to make the codes easy to read.