Emergency Default Mode, Function - GF27.60-P-3012AHE
TRANSMISSION 722.9 (except 722.930) in MODEL 205
Function requirements for limp-home mode, general
- Circuit 87 (connected circuit 15) ON
- Circuit 61 (engine running)
Limp-home mode, general
In order to guarantee a safe driving condition and to avoid damage to the transmission, the fully integrated transmission control unit (Y3/8n4) switches to limp-home mode in the event of critical faults. The malfunction with the associated fault code is stored in the fault memory and communicated to the CDI control unit (N3/9) or the ME-SFI [ME] control unit (N3/10) via the drive train CAN (CAN C1).
Additionally, the CDI control unit or the ME-SFI [ME] control unit sends an indicator lamp request via engine CAN (CAN C) to the powertrain control unit (N127). This sends the request over the chassis FlexRay (Flex E) and with the electronic ignition lock control unit interface (N73) over the user interface CAN (CAN HMI) to the instrument cluster (A1). The instrument cluster 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.
It is possible to engage gear ranges "R" and "D" after engaging gear range "P".
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.
Diagnosis
Up to 16 faults can be stored simultaneously in the fault memory. These can be read out using Xentry diagnostics.
| Overview of system components for automatic transmission (AT) | GF27.10-P-9992AHE |