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Preheat, Function - GF15.20-P-3005OGF

ENGINE 642.8 in MODEL 166 

as of model year 2016 

ENGINE 642.8 in MODEL 292 

Function requirements for preheating, general points 

Preheating, general points 

The preglowing system warms up the engine combustion chambers to the ignition temperature required for ignition of the fuel/air mixture.

IMPORTANT

At cold temperatures the vent line heater element (R39/1) is actuated by the CDI control unit (N3/9). This prevents freezing of the crankcase ventilation system and any associated engine damage.

Function sequence for preheating 

The function sequence is subdivided into the following steps:

Function sequence for preglowing 

The CDI control unit receives the message "circuit 15 ON" from the electronic ignition lock control unit (N73) via chassis CAN 1 (CAN E1). The CDI control unit reads in the engine oil temperature via the engine oil temperature sensor (B1) and then actuates the glow output stage (N14/3) via the drive LIN (LIN C1) depending on the coolant temperature, and the preglow indicator lamp (A1e16) via chassis CAN 1, the electronic ignition lock control unit and chassis CAN 2 (CAN E2). The glow output stage then actuates the glow plugs of cylinders 1 to 6 (R9/1 to R9/6) at the positive side.

IMPORTANT

If a fault occurs in the preglow system, at the glow plugs or on the lines, this is indicated by the preglow indicator lamp and also stored in the CDI control unit.

Function sequence for start-ready glowing 

Start-ready glowing ensures an adequately high temperature until the engine finally begins to run. If the CDI control unit receives the information "circuit 50 ON" from the electronic ignition lock control unit via chassis CAN 1, it will continue to actuate the glow output stage for a certain time irrespective of the engine oil temperature, and the glow output stage in turn actuates the glow plugs.

After the start-ready temperature of 1250°C has been reached, the preglow indicator lamp goes out.

Function sequence for start-up glowing 

Start-up glowing is used to stabilize the cold start speed of the engine. If the CDI control unit receives the "circuit 61 ON" information from the alternator (G2) via the drive LIN, the glow output stage is actuated over the drive LIN. The glow output stage then actuates the glow plugs. In this way the first working cycles and the eventual running of the engine are supported.

IMPORTANT

For alternators with alternator interface is the line "circuit 61" is not needed. Using the information that the CDI control unit receives via the alternator interface, the circuit 61 signal is simulated in the CDI control unit and output via an output stage (e.g. for the instrument cluster (A1)).

Function sequence for afterglowing 

Afterglowing improves engine running after a cold start and the engine warm-up characteristics.

After a successful engine start, the CDI control unit reads in the engine oil temperature via the engine oil temperature sensor and actuates the glow plugs via the glow output stage dependent on the engine oil temperature.

Function sequence for diagnostic glowing 

This function is used to energize the glow plugs to a low temperature level and a system diagnosis is performed. This function is activated during troubleshooting and when the preglow system has been inactive for a long period (no preheating required owing to high ambient temperature).

Function sequence for diesel particulate filter (DPF) preheating 

The DPF glowing function is used to raise the load and to stabilize combustion and thus to assist regeneration of the DPF. To do this the CDI control unit receives the message "circuit 50 ON" via chassis CAN 1 from the electronic ignition lock control unit. The CDI control unit then actuates the glow output stage through the drive-LIN.

Function sequence for emergency glowing 

If a communication problem occurs between the CDI control unit and the glow output stage, meaning that the glow output stage does not recognize any activity for 2 s after activation via circuit 87, the emergency glowing function is actuated for 180 s. If communication is missing during a glowing process for more than 250 ms then the glowing process will be continued for 180 s.

IMPORTANT

If no new glow request is received from the CDI control unit then emergency glowing stops after 180 s.

  Electrical function schematic for preheating   PE15.20-P-2051-97NBD 
  Overview of system components for common rail diesel injection (CDI)   GF07.16-P-9997OGF
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