Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Thermal Management, Function - GF07.10-P-1012MNB
Engine 178.9 In Model 190
Function requirements, general
- Engine running (circuit 87M On)
Thermal management, general
The ME-SFI [ME] control unit (N3/10) regulates the coolant temperature of the engine. The following advantages arise from this:
- Rapid attainment and maintaining of the optimum operating temperature
- Reduction of the exhaust emissions
- Fuel savings (up to approx. 4 %)
- Improved heating comfort
The ME-SFI [ME] control unit evaluates the following variables for heat management:
- Engine oil temperature detected by engine oil temperature sensor (B1)
- Coolant temperature detected by coolant temperature sensor (B11/4)
- Charge air temperature detected by left charge air temperature sensor (B17/14) and right charge air temperature sensor (B17/15)
- Engine load detected by pressure sensor downstream of left throttle valve (B28/22) and pressure sensor downstream of right throttle valve (B28/23)
- Accelerator pedal actuation detected by accelerator pedal sensor (B37)
- Engine speed detected by crankshaft Hall sensor (B70)
- Control unit temperature detected by temperature sensor in ME-SFI [ME] control unit
- Status of air conditioning
The climate control control unit (N22/1) transmits the status of the air conditioning system via the interior CAN (CAN B), AMG Gateway control unit (N93/9), chassis CAN 1 (CAN E1), as well as the powertrain control unit (N127) and drive train CAN (CAN C1) to the ME-SFI [ME] control unit.
- Vehicle speed
The instrument cluster (A1) transmits the vehicle speed via the user interface CAN (CAN HMI), the AMG Gateway control unit, the chassis CAN 1, the powertrain control unit, and the drive train CAN to the ME-SFI [ME] control unit.
- Wheel speeds
The Electronic Stability Program control unit (N30/4) transmits the wheel speed via the chassis CAN 1, powertrain control unit, and drive train CAN to the ME-SFI [ME] control unit.
- Transmission oil temperature
The transmission oil temperature sensor records the transmission oil temperature. The dual-clutch transmission control unit (N15/13) transmits the status of the transmission oil temperature via the drive train CAN to the ME-SFI [ME] control unit.
High-temperature circuit and oil cooling, shown in model 190.381
High-temperature circuit and oil cooling, shown in model 190.379
The subsequent function sequence is subdivided into the following sections:
- Heating the two-valve thermostat
- Fan control
- Air regulation system (model 190.379/380/477/478/480)
- Overheating protection
- Heating system switch-off
Heating the two-valve thermostat
The temperature of the coolant can be controlled variably by the heatable two-slide thermostat. There is a coolant thermostat heating element in the two-slide thermostat which is actuated as required by the ME-SFI control unit using a ground signal.
The two-slide thermostat can assume five positions:
- Stationary coolant
- Bypass mode
- Mixed mode
- Radiator operation
- Fail/Safe position
Stationary coolant
At a coolant temperature above 80°C and an engine RPM of less than 3000 RPM, both coolant outlets of the two-valve thermostat are closed completely.
Shortening of the engine warm-up phase by stationary coolant leads to fuel saving and therefore reduction of the CO2
output.
Bypass mode
- De-energized heating element (coolant temperature 80 to 105°C)
- Energized heating element (coolant temperature 40 to 65°C)
In partial-load range, the coolant temperature can be raised to approx. 105°C (heating element de-energized). Therefore the friction power can be improved due to a higher engine oil temperature and the mixture formation improved due to less fuel condensation on the cylinder barrels.
Mixed mode
- De-energized heating element (coolant temperature 105 to 120°C)
- Energized heating element (coolant temperature 65 to 90°C)
Radiator operation
- De-energized heating element (coolant temperature above 120°C)
- Energized heating element (coolant temperature above 90°C)
Through heating the two-slide thermostat (heating element energized) this opens and the coolant is led through the engine radiator. For wide open throttle the two-slide thermostat is very quickly opened. The coolant temperature can be lowered whereby the best possible engine cooling and knock-free combustion are achieved.
Fail/Safe position
The fail-safe position is initiated if the coolant is stationary and the engine RPM is above 3000 RPM in order to avoid damage. The coolant is passed back over the differential pressure disc to the engine (short circuit).
Fan control
The powertrain control unit actuates the fan motor (M4/7) via the drivetrain LIN (LIN C3). The ME-SFI [ME] control unit transmits the fan nominal speed via drive train CAN to the powertrain control unit. If the powertrain control unit does not receive a valid fan request, the fan motor is actuated at maximum RPM via the drivetrain LIN. In the case of a fault in the signal line (loss of frequency) by the powertrain control unit, the fan motor switches itself to the maximum RPM (fan emergency mode).
The climate control control unit transmits the status of the air conditioning system and a fan request via the interior CAN, AMG Gateway control unit, and chassis CAN 1 to the powertrain control unit.
Delayed fan switch off:
The fan motor runs on for up to 5 minutes with "ignition OFF" when the coolant temperature, the temperature of the ME-SFI [ME] control unit or a thermal input integral calculated based on an engine load, coolant temperature, vehicle speed and outside temperature (averaged over the last 6 min) has exceeded a prescribed threshold value. If the battery voltage drops down a lot, the delayed fan switch off is stopped.
The delayed fan switch off is not broken off by "ignition ON". When starting the engine in delayed fan switch off the fan regulation for normal operation is suppressed until the delayed fan switch off is completed.
Air regulation system (model 190.379/380/477/478/480)
The air regulation system is located immediately behind the front skirt and consists of a frame with vertically-arranged slats, that close or open the lower openings at the front of the vehicle towards the engine radiator. The clutch packs are moved via the linkage of the left air regulation system actuator motor (M108/3) and right air regulation system actuator motor (M108/4). The complete opening or closing takes about 1 s. The released openings enable the air mass flow to be routed straight to the engine radiator without any leakages. In the case of closed openings the driving and aerodynamics are improved greatly.
In a normal case the disks close off the openings in the vehicle front. The aerodynamic drag is low. The air mass flow is steered in the direction of the underfloor in order to maintain the uplift on the front axle. Also for high speeds, when braking and in sharp curves the openings are closed. If the cooling air requirements are particularly high, the ME-SFI [ME] control unit transmits the request for actuation of the air regulation system actuator motors via the engine CAN (CAN C) to the powertrain control unit. The powertrain control unit then actuates the air regulation system actuator motors via the drive train LIN accordingly.
The ME-SFI [ME] control unit evaluates the following signals for this purpose:
- Engine oil temperature
- Coolant temperature
- Charge air temperature
- Engine load
- Accelerator pedal actuation
- Engine speed
- Status of air conditioning
- Vehicle speed
- Transmission oil temperature
- Outside temperature
The front SAM control unit with fuse and relay module (N10/1) transmits the outside temperature via the powertrain CAN to the ME-SFI [ME] control unit.
The maximum cooled air to the engine radiator flows through the opened disks.
View of air regulation system; shown is: model 190.379
Overheating protection
In a case of thermal overload the overheating protection protects the catalytic converters against engine damage and overheating damage.
To this the ME-SFI [ME] control unit reads in the signals of the coolant temperature sensor and the engine oil temperature sensor.
The following measures are be taken by the ME-SFI [ME] control unit to avoid overheating of the engine:
- A characteristics map-dependent ignition angle setting in the direction "retarded", dependent on the engine load and-engine speed, as of a coolant temperature of approx.90°C and a charge air temperature of approx.20°C
- Characteristics map-dependent reduction of the injection quantity for a coolant temperature of more than 106°C
- Regulation of the injection period through actuation of:
- Left quantity control valve (Y94/1)
- Right quantity control valve (Y94/2)
- Cylinder 1 fuel injector (Y76/1)
- Cylinder 2 fuel injector (Y76/2)
- Cylinder 3 fuel injector (Y76/3)
- Cylinder 4 fuel injector (Y76/4)
- Cylinder 5 fuel injector (Y76/5)
- Cylinder 6 fuel injector (Y76/6)
- Cylinder 7 fuel injector (Y76/7)
- Cylinder 8 fuel injector (Y76/8)
- Reduced opening of the throttle valves via the left throttle valve actuator motor (M16/60m1) and the right throttle valve actuator motor (M16/61m1), depending on the engine load and rotational speed
- Actuation of the coolant thermostat heating element
If the engine oil or coolant temperature is too high, a warning message in instrument cluster is shown. The ME-SFI control unit sends the respective signal via the powertrain CAN, powertrain control unit, chassis CAN 1, AMG gateway control unit and user interface CAN to the instrument cluster.
Heating system switch-off
To heat up the engine more quickly, the ME-SFI control unit switches off the heating system coolant circuit by actuating the heating system shutoff valve (Y16/2).
| Electrical function schematic for heat management | PE07.10-P-2712-97HBA | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNB |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.