Computers and Control Systems: Description and Operation

The J220 Engine Control Module (ECM) is equipped with a DTC memory.

If malfunctions occur in the sensors and components being monitored, they will be stored in DTC memory together with an indication of the type of malfunction.

After evaluating incoming data, the ECM can pick between 149 different possible DTC's and store them until the contents of DTC memory is intentionally erased. See 'Computers and Control Systems, Testing and Inspection, Procedures, Diagnostic Trouble Code (DTC) Test Procedures.' Testing and Inspection

Malfunctions which only occur sporadically will have the words "sporadic malfunction" shown on the print out. These malfunctions will be indicated on the display by the suffix "/SP". These malfunctions can be caused by a loose terminal or a briefly open circuit. If a sporadic malfunction does not occur again within 40 warm-up phases (if engine started below 50 °C Engine Coolant Temperature and switched OFF above 72 °C), it will automatically be erased from DTC memory.

Stored malfunctions can be displayed using the VAG 1551/1552 Scan Tool See 'Computers and Control Systems, Testing and Inspection, Procedures, How to Pull and Clear Diagnostic Trouble Codes (DTC's).' Testing and Inspection

- Display the Readiness code See 'Computers and Control Systems, Testing and Inspection, Procedures, Other Scan Tool Functions, Displaying and Setting Readiness Code.' Testing and Inspection

If DTC memory was erased or if the ECM was disconnected from Battery positive
- Set the Readiness code See 'Computers and Control Systems, Testing and Inspection, Procedures, Other Scan Tool Functions, Displaying and Setting Readiness Code.' Testing and Inspection