Important Notes Regarding On-Board Diagnostics

Mercedes Benz requires the use of special tools for reading Diagnostic Trouble Codes (DTC's) from the various control modules.

The Diagnostic Module can only be accessed with a Generic Scan Tool or with the Mercedes Hand-Held Tester (HHT). DTC readout of the Diagnostic Module via the impulse counter scan tool or via the LED pushbutton switch has been eliminated in this version of the Diagnostic Module.

All other Control Modules (HFM-SFI, CC/ISC, etc.) require an impulse counter scan tool or the Mercedes Hand-Held Tester (HHT).

Note: Mercedes Benz does not supply procedures for reading Diagnostic Trouble Codes (DTC's) without use of the special tools listed above.


Diagnosis with Generic Scan Tool (Only possible on Diagnostic Module [OBD II] DTC's)
1. Extract fault codes from Diagnostic Module (N59/1) via the OBD II Diagnostic Connector (X11/22). Refer to "How to Read Diagnostic Trouble Codes (DTCs)" under the system to be diagnosed.
2. Find correct fault code/diagnostic trouble code (DTC) in the Diagnostic Module code chart and test suspect circuit or component as indicated in the "Test Step/Remedy" column.
3. Repair defective circuit or component.
4. Erase fault codes from Diagnostic Module according to scan tool manufacturers instructions.
5. Test drive vehicle and recheck fault codes.

Diagnosis with HHT or Impulse Counter Scan Tool
1. Extract fault codes from each individual control module (Not possible to extract Diagnostic Module codes with the impulse counter scan tool). Refer to "How to Read Diagnostic Trouble Codes (DTCs)" under the system to be diagnosed.
2. Find correct fault code (DTC) in the applicable code chart and test suspect circuit/component as indicated in the "Test Step/Remedy" column.
3. Repair defective circuit or component.
4. Erase fault codes from each individual control module.
5. Test drive vehicle and recheck fault codes.