GF27.60-P-3012AHT Emergency Default Mode, Function

GF27.60-P-3012AHT Emergency Default Mode, Function
- TRANSMISSION 722.931 in MODEL 221.074 /174, 216.374

Function requirements for limp-home mode, general

^ Circuit 87 ON
^ Circuit 61 (engine running)

Limp-home mode, general

To guarantee a reliable driving condition and to avoid any damage to the transmission, the fully integrated transmission control unit (VGS) (Y3/8n4) switches to the limp-home mode for critical malfunctions and the malfunction is stored in the fault memory along with the assigned fault code.

The malfunction is sent to the ME-SFI [ME] control unit (N3/10) as a signal by the fully integrated transmission control unit (VGS) over the drive train CAN (CAN C).

The ME-SFI [ME] control unit also sends the signal over the chassis CAN (CAN E) to the central gateway control unit (N93). The central gateway control unit then routes the signal over the central-CAN (CAN F) to the instrument cluster (A1), which then activates the engine diagnosis indicator lamp (A1e58).

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

After gear range "P" is engaged, gear range "R and D" can also be engaged.

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

If hydraulic faults occur, the transmission remains in the respective gear.

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.

Diagnosis

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