Flow chart
| A | hands-free access control unit |
|---|---|
| BB00 | Battery |
| BFDB | Fuse box from battery |
| BSI1 | built-in systems interface |
| CA00 | ignition switch |
| PSF1 | engine compartment connector board-fuse box |
| 0004 | Instrument panel |
| 1158 | pre-postheating control unit |
| 1160 | preheater plugs |
| 1220 | engine coolant temperature sensor |
| 1240 | induction air temperature sensor |
| 1312 | inlet air pressure sensor |
| 1313 | engine speed sensor |
| 1320 | engine ECU |
| 8235 | Engine starting switch |
| connection number | signal | transmitter/receiver | nature of signal |
|---|---|---|---|
| 1 | engine starting switch information | 8235 / A | by wire |
| 2 | engine starting request | A / BSI1 | CAN-B |
| engine starting switch information | |||
| 3 | engine coolant temperature information | 1220 / 1320 | by wire |
| 4 | engine speed information | 1313 / 1320 | by wire |
| 5 | information: Inlet air pressure | 1312 / 1320 | by wire |
| 6 | information: Inlet air temperature | 1240 / 1320 | by wire |
| 7 | activation of the pre-postheating plugs | 1158 / 1160 | by wire |
| 8 | information: pre-post heating unit control fault | 1158 / 1320 | by wire |
| control of the pre-postheating unit | 1320 / 1158 | analogue | |
| 9 | request for display of the preheating warning lamp | 1320 /BSI1 | CAN-C |
| 10 | control of displaying of the preheating warning lamp | BSI1 / 0004 | CAN-B |
Pre-heating
Role
The preheater plugs enable the temperature to rise rapidly in the combustion chambers prior to the engine being started, when starting from cold or when the outside temperature is low
Role of preheating
- To facilitate starting from cold (the air is heated up to enable the injected diesel fuel to combust more easily)
- To reduce smoke emissions (the heated air reduces the incidence of unburnt gases)
NoteThe change from preheating to postheating occurs without interruption during the starting phase
Function
The engine ECU controls the pre-postheating control unit by means of an open cycle ratio
The electrical supply of the preheater plugs is via the pre-postheating control unit, as a function of the commands from the engine ECU
The temperature of the coolant must be 60°C or below in order for the preheating to be activated
The maximum duration for which the preheater plug is supplied with power is 20 seconds if the engine does not start
The preheating times are determined by the engine ECU as a function of the following parameters
- Coolant temperature
- Induction air temperature sensor
Post heating
Role
Within the first few seconds of the engine starting, the temperature in the combustion chambers does not permit a combustion of sufficient quality, this causing the engine to be unstable at idle and to emit excessive pollution
Role of postheating
- To prolong the operation of the preheater plugs after the cold starting phase
- To guarantee the correct quality of combustion after starting
- Reducing the emissions of pollutants in the first few minutes after starting
- To stabilise the engine at idle
- To reduce blue smoke emissions
Function
The engine ECU controls the pre-postheating control unit by means of an open cycle ratio
The unit supplies the pre-heater plugs with power in accordance with the orders of the engine management ECU
If a pre-post heating control unit failure occurs, the engine management ECU memorises a fault
Postheating times are determined by the engine ECU depending on the engine coolant temperature
Activation conditions
The postheating is activated in the following conditions
- The engine speed is 350 rpm or higher
- The temperature of the coolant is below 70°C
Conditions of deactivation
The preheater plugs are supplied with power for a maximum duration of 300 seconds