Computers and Control Systems: Description and Operation

GENERAL INFORMATION

The Motronic Engine Control Module (ECM) features On-Board Diagnostic (OBD) capability. If problems occur at monitored sensors or components, they are stored in Diagnostic Trouble Code (DTC) Memory.

Typical Fault Indicator Light:

The Motronic ECM after evaluating the information, differentiates between 29-30 possible malfunctions and stores them until DTC Memory is erased.

The Motronic ECM turns on the Malfunction Indicator Lamp (MIL) anytime a fault code is stored. The MIL remains lit anytime the engine is running until the fault is repaired and the DTC memory is cleared.

The Motronic ECM is equipped with diagnostic capability for 10-12 possible Output Diagnostic Test Mode (DTM) checks.

Vehicles equipped with the V8 MOTRONIC engine management system have Data Link Connectors (DLC) for accessing the DTC memory and activating the DTM checks.

^ DTC Memory should ONLY be activated with the engine running, if possible

^ Malfunctions which occur occasionally are classified as intermittent.

^ If a malfunction is present for a sufficient time, it is stored as static. If a condition appears momentarily or for insufficient time to be classified as static it will be stored as intermittent. This process repeats itself continuously

^ If the intermittent malfunction does not re-occur during the next 50 engine starts. it will be automatically erased from DTC Memory

^ If several malfunctions occur at the same time, check ground connections at the rear of the engine and between left engine block and left long member for corrosion or damaged connections, repair or replace as necessary

^ Output DTM checks can ONLY be performed with the engine NOT running

^ To fully access the vehicles OBD capabilities requires the VAG 1551 Scan Tool

ECM Functions

Permanent DTC memory

Output DTM checking

Engine basic setting

Data Output modes:

- Rapid data transfer (VAG 1551 only)

- Blink code output at the MIL

- Blink code output at LED Test Light