Emergency Default Mode, Function - GF27.60-P-3012RR
Model 190 With Transmission 700.4
Limp-home mode, general
On the dual clutch transmission the limp-home mode function can be divided into the following partial functions:
- Transmission limp-home mode, part Transmission even/odd
- Transmission limp-home mode, power-free state
- Transmission limp-home mode, Transmission overtemperature
- Transmission limp-home mode for defective park pawl system
The dual clutch transmission control unit (N15/13) monitors the status of the transmission control by means of the following sensors:
- Clutch pressure sensor K1 (Y3/11b1)
- Clutch pressure sensor K2 (Y3/11b2)
- System pressure sensor (Y3/11b3)
- Temperature sensor module (Y3/11 b5)
- Shift fork position sensor 1 (Y3/12s1)
- Shift fork position sensor 2 (Y3/12s2)
- Shift fork position sensor 3 (Y3/12s3)
- Shift fork position sensor 4 (Y3/12s4)
- Pressure distributor position sensor (Y3/12s6)
- Park pawl position sensor (Y3/12s7)
- Gear set group oil temperature sensor (Y3/13b2)
- Dual clutch transmission output shaft RPM sensor (Y3/13n1)
- Dual clutch transmission hollow shaft RPM sensor (Y3/13n2)
- Dual clutch transmission internal shaft RPM sensor (Y3/13n3)
- Engine speed sensor (Y3/13n4)
The dual clutch transmission control unit checks and actuates the following actuators electrically:
- System pressure regulation valve (Y3/11y3)
- Clutch K1 regulation valve (Y3/11y4)
- Clutch K2 regulation valve (Y3/11y5)
- Clutch cooling K1 regulation valve (Y3/11y6)
- Clutch K1 emergency shift switchover valve (Y3/11y7)
- Clutch K2 emergency shift switchover valve (Y3/11y8)
- Clutch cooling K2 regulation valve (Y3/11y10)
- Shift rods A regulation valve (Y3/12y1)
- Shift rods B regulation valve (Y3/12y2)
- Shift rods C regulation valve (Y3/12y3)
- Shift rods D regulation valve (Y3/12y4)
- Pressure distributor switchover valve (Y3/12y5)
- Park pawl switchover valve (Y3/12y6)
- Park pawl locking solenoid (Y3/13b1)
The dual clutch transmission (DKG) control unit checks the plausibility of sensor and actuator values.
The dual clutch transmission control unit monitors and additionally performs a plausibility check on the signals that are received via the CAN bus.
The temperature sensor module is comprised of the following temperature sensors:
- Clutch temperature sensor K2 (Y3/11 b6)
- Oil cooler temperature sensor (Y3/11 b7)
- Clutch temperature sensor K1 (Y3/11 b8)
Transmission limp-home mode, part Transmission even/odd
In the event of failure of a gear cylinder or a clutch in the sub-transmission, individual gears or the following sub-transmission are not available:
- Sub-transmission 1-3-5-7
- Sub-transmission R-2-4-6
The vehicle can still be driven to a qualified specialist workshop.
Display messages
| Display message in multifunction display (A1p13) | Status | Effect/reaction |
|---|---|---|
| None | The part transmission 1-3-5-7 is not available. | The engine diagnosis indicator lamp (A1e58) is actuated. The transmission is in limp-home mode. |
| "Reversing not Possible, Service Required" (in red lettering) | Part transmission R-2-4-6 is not available. | The engine diagnosis indicator lamp is actuated Reverse gear can no longer be engaged. Shift comfort is restricted. The transmission is in limp-home mode. |
Transmission limp-home mode, power-free state
The complete frictional connection has failed.
| Display message in multifunction display | Status | Effect/reaction |
|---|---|---|
| "Stop vehicle Engage gear range P" (in red lettering), transmission symbol | Failure of complete power flow functionality (e.g. system pressure not present, both clutches defective, gear actuator system defective, extreme overtemperature in transmission) | The vehicle rolls without frictional connection, has no more traction permanently The engine diagnosis indicator lamp is actuated The vehicle must be parked to suit the traffic conditions A qualified specialist workshop must be contacted. |
Transmission limp-home mode, Transmission overtemperature
There is a fault in the oil cooling system. The hydraulic fluid, oil of from set group or the dual clutch is overheated.
The dual clutch transmission control unit determines the oil temperature of the gear set group via the gear set group oil temperature sensor, and the temperature of the hydraulic fluid via the oil cooler temperature sensor and a temperature model for the transmission oil sump.
| Display message in multifunction display | Status | Effect/reaction |
|---|---|---|
| "Transmission cooling fault" (in white lettering), transmission symbol | The oil cooling system coolant circulation pump (M13/7) is defective. | There is a risk of overheating. In the multifunction display, select the AMG menu and check the transmission oil temperature. High load such as, for example, avoid dynamic driving style. At transmission oil temperatures below 120°C continue driving to the next qualified specialist workshop. |
| "Transmission oil overheating Continue with care" (in white lettering), transmission symbol | The hydraulic fluid and/or oil of the gear set group has/have exceeded a specified temperature threshold. | The automatic transmission fluid is overheated. The manual transmission mode "M" and gear limitation are no longer available. The engine power is reduced corresponding to overheating. Allow the automatic transmission fluid to cool down by adopting a defensive driving style. |
Transmission limp-home mode for defective park pawl system
The park pawl locking solenoid hangs up, or the piston in the park pawl hydraulic cylinder is blocked.
| Display message in multifunction display | Status | Effect/reaction |
|---|---|---|
| "Park pawl defective Apply parking brake" (in red lettering), large red "P" as symbol | The park pawl locking solenoid hangs up, or the piston in the park pawl hydraulic cylinder is blocked. The park pawl can no longer be engaged or released. | The vehicle is not secured to prevent it from rolling away. The driver can activate the electric parking brake (EFB). The electric parking brake control unit (N128) reads in the signals for accelerator pedal sensor, engine speed and the status of the gear range and implements the request to activate the parking brake by actuating the corresponding actuator motors. The EFB is activated automatically when vehicle is at a standstill or the button "P" is pressed at a vehicle speed of v < 8 km/h. If the EFB cannot be applied, the message "Parking brake nonfunctional" appears in the multifunction display. It can be reckoned that the vehicle is not secured to prevent it from rolling away. |
| Electrical function schematic for limp-home function | PE27.19-P-2065-97HBA |
| Overview of system components for dual clutch transmission | GF27.10-P-9994RR |