Characteristics of On Board Diagnostic (OBD)

Characteristics Of On Board Diagnostic (OBD)

Engine Control Modules (ECM) and Transmission Control Module (TCM) are equipped with a DTC memory.

Malfunction recognition
If malfunctions occur at the emission relevant systems or components, they are stored in DTC memory with a description of the malfunction type.

Control modules differentiate between different DTCs after evaluating the information.

The stored malfunctions can be checked with a standard diagnostic tester, Diagnostic mode 3: Check DTC memory.

When harness connectors are disconnected from the Engine Control Module (ECM) or Transmission Control Module (TCM), or the battery is disconnected, all adaptation values in the control modules are erased. DTC memory content will remain intact however. If the engine is started after this, rough, uneven idle can result. In this case, the readiness code must be generated again.

The following work steps must be performed in the described sequence after the malfunction(s) have been repaired:
1. Check DTC memory.
2. Erase DTC memory.
3. For completion, generate readiness code.