On Board Diagnostic, Features

The Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) J248 for the diesel direct fuel injection (DFI) system is equipped with a Diagnostic Trouble Code (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 malfunction type.

After evaluating the information, the ECM decides between different malfunctions Diagnostic Trouble Code (DTC) table → DTC table: VAG codes  and stores them until the DTC memory is erased.

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 50 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 below 49 ° C (120 ° F) and runs continuously until the temperature reaches 71 ° C (160 ° F).

Malfunctions can be read with Scan Tool (ST) VAG1551 , VAG1552 or VAS5051 → Diagnostic Trouble Code (DTC) memory, checking and erasing  .

Fig 1: Locating MIL & Glow Plug Indicator Lamp

Courtesy of VOLKSWAGEN UNITED STATES, INC.

If malfunctions that influence exhaust emissions are recognized, Malfunction Indicator Lamp (MIL) K83 - 1  - illuminates.

If malfunctions are recognized that affect driveability, the glow plug indicator lamp - 2  - blinks.

The stored malfunctions can be read out with the fault reader VAG1551 , the vehicle system tester VAG1552 , or with VAS5051 → Diagnostic Trouble Code (DTC) memory, checking and erasing  .

The fault memory must be erased after the faults have been eliminated → Diagnostic Trouble Code (DTC) memory, checking and erasing  and the readiness code must be set again → Readiness code, setting  .