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Thermal management, function - GF07.10-P-1012OGG

ENGINES 642.8 in MODEL 164.1 as of model year 2009/YoM 08 model refinement package 

ENGINES 642.8 in MODEL 164.8, 251.1 as of model year 2009/YoM 08 

ENGINES 642.8 in MODEL 251.0/1 as of model year 2011/YoM 10 model refinement package 

Function requirements for thermal management, general points 

Thermal management, general points 

The coolant temperature of the engine is regulated by the controlled thermal management from CDI control unit (N3/9). This has the following advantages:

Thermal management is performed according to the following sensors and signals:

Function sequence for thermal management 

The thermal management system is described in the following steps:

Function sequence for heating the coolant thermostat 

The CDI control unit actuates the two-disk thermostat heating element (R48) (dependent on the performance map) depending on the operating conditions (except code (U42) BlueTEC (SCR) diesel exhaust treatment and with code (494) USA version) using a ground signal.

The voltage is supplied through "circuit 87".

When heated, the two-disk thermostat opens in the coolant thermostat. In this way the coolant temperature of 55 to 110°C is regulated via the duty cycle.

Function sequence for maximum heating combustion 

For the "hot burning process" more heat is conducted into the coolant on the engine side due to a new combustion strategy.

The following function conditions must be met simultaneously:

During the hot burning process a significantly higher exhaust temperature is achieved through 2 preinjections by the fuel injectors (Y76) and a later main injection generates an increased exhaust temperature. More heat is given up to the coolant inside the engine in combination with the exhaust gas recirculation (AGR) which allows more rapid attainment of the optimum operating temperature and improved warming of the vehicle interior.

Function sequence for tank protection 

Increasing the fuel pressure via the high-pressure pump from 4.5 bar up to 1800 bar also increases the temperature of the fuel.

To protect the fuel tank from overheating, the CDI control unit reads in the fuel temperature sensor and thus monitors the temperature of the fuel delivered to the high-pressure pump.

If the temperature of the fuel to be delivered to the high-pressure pump rises above 90°C, the CDI control unit increases the injection quantity and the rail pressure using the quantity control valve (Y74). This causes the fuel to be less compressed.

The quantity control valve (Y94) diverts excess fuel back into the fuel tank.

When the temperature of the fuel delivered to the high-pressure pump drops below 90°C, the tank protection function is deactivated by the CDI control unit.

Function sequence for fan control 

The CDI control unit actuates the engine and air conditioning electric suction fan with integrated control (M4/7). The specified fan speed is set by the CDI control unit by means of a pulse width modulated signal (PWM signal).

The duty cycle of the PWM signal is 10 to 90%.

This means, for example:

10% Fan motor "OFF"

20% Fan motor "ON", minimum RPM

90% Fan motor "ON", maximum RPM

If actuation is faulty, the air fan rotates at the maximum rotational speed (fan emergency mode).

The AAC [KLA] control and operating unit (except code (581)

Comfort automatic air conditioning) or the comfort AAC control and operating unit (with code (581) Comfort automatic air conditioning) transfers the status of the air conditioning to the CDI control unit via the interior and engine compartment CAN.

Delayed fan switch off 

With "ignition OFF", the fan motor runs on for up to 5 min. if the coolant temperature or engine oil temperature (calculated from the temperature model) has exceeded the specified maximum values. The PWM signal duty cycle is 40% maximum while the delayed fan switch-off is active.

If the battery voltage drops too much during this time, delayed fan switch-off is stopped.

Function sequence for overheating protection 

The overheating protection protects against engine damage if there is a thermal overload. At a coolant temperature above 106°C the injection quantity is reduced based on the characteristic maps stored in the CDI control unit.

Reduction occurs depending on the coolant temperature and oil temperature.

To this end, the CDI control unit reads in the coolant temperature sensor (), oil temperature sensor (B1) and the temperature sensor upstream of the turbocharger (B19/11) (turbocharger protection).

After evaluating the input signals, the CDI control unit regulates the fuel pressure in the rails via the quantity control valve and the pressure regulating valve, and controls the injection timing by actuating the fuel injectors.

REFER TO SYSTEM WIRING DIAGRAMS Electrical function schematic for thermal management Model 164   PE07.10-P-2712-97MAA
Model 251   PE07.10-P-2712-97RAA
  Component description for instrument cluster A1   GF54.30-P-6000GM
  Component description for CDI control unit N3/9   GF07.16-P-6000OGU 
  Component description for automatic air conditioning control and operating unit N22 Except code (581) Comfort automatic air conditioning GF83.40-P-3000GM
  Component description for comfort automatic air conditioning control and operating unit N22/7 with code (581) Comfort automatic air conditioning GF83.40-P-3010GM
  Component description for ESP control unit N47-5   GF42.45-P-5118GM
  Component description for central gateway control unit N93   GF54.21-P-4170GM
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