Description of On-Board Diagnostics

General Information For 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 DTC tables.

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

When connectors are disconnected from the Engine Control Module (ECM) or the batteries are disconnected, all adaptation values in the control module are erased. DTC memory content will remain intact however. If the engine is started after this, rough, uneven idle can result for a short time. 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, Diagnostic mode 3: Check DTC memory.
2 - Erase DTC memory, Diagnostic mode 4:. Refer to Diagnostic Mode 4: Reset/Erase Diagnostic Data.
3 - For completion, Generate readiness code. Refer to Readiness Code, Generating.