Limp-Home Mode, Function - GF27.60-D-3012HAG

TRANSMISSION 722.9 in MODEL 906 

Function requirements for limp-home mode, general 

• "Circuit 87 ON"
• "Circuit 61 ON" (engine running)

Limp-home mode, general 

In order to ensure a safe driving condition and to avoid damage to the transmission, the control unit (Y3/8n4) switches to limp-home mode in the event of critical faults.

The fault is stored in the fault memory with the assigned fault code and the EOBD indicator lamp (A1e17) in the instrument cluster (A1) is actuated.

In addition, the fault is transmitted to the CDI control unit (N3/28) (with engine 651) or CDI control unit (N3/30) (with engine 642) via the engine compartment CAN (CAN C).

In the event of a hardware fault, all control solenoid valves are switched off and the transmission switches to 6th gear.

After engaging gear range "P" it is possible to engage gear range "R" or "D".

In gear range "D", the transmission shifts to 2nd gear.

If hydraulic faults occur, the transmission remains in the gear currently engaged.

In the event of control solenoid valve faults, the affected gear is disabled and no longer actuated.

As a result the vehicle can be brought to the nearest Mercedes-Benz service operation.

Up to 16 faults can be stored simultaneously in the fault memory. These can be read out using the Diagnosis Assistance System (DAS).