Computers and Control Systems: Description and Operation

- The Engine Control Module (ECM) for the Diesel direct injection system is equipped with a Diagnostic Trouble Code (DTC) memory.
- The Engine Control Module differentiates (after evaluating all obtainable information) between more than 40 different possible malfunctions See DTC table. Testing and Inspection
- 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.
- Malfunctions which only occur sporadically will have the addendum "sporadic" on the print out. These malfunctions will be indicated on the display by the addendum "/SP" The cause of sporadic malfunctions can be e.g. a loose terminal or a brief open circuit. If a sporadic malfunction does not occur again within 40 warm-up cycles, it will be erased from DTC memory.
- The warm-up cycle is designated by each engine start, beginning at an Engine Coolant Temperature of 49 °C maximum and operates at a continuous temperature of 71 °C.







- If malfunctions that influence exhaust emissions are recognized, Malfunction Indicator Lamp (MIL) -1- lights up.
- If malfunctions are recognized that affect driveability, then the glow period warning lamp -2- flashes.
- Stored malfunctions can be displayed using the VAG 1551/1552 Scan Tool. Testing and Inspection
- DTC memory must be erased after malfunctions have been eliminated.
- After erasing DTC memory the readiness code must be created again.