S07.10-0055-79
Block diagram |
A9/10 | Refrigerant compressors with magnetic clutch | N154 | Climate control control unit (with code H06 (Air conditioning system) or with code HH4 (THERMOTRONIC automatic air conditioning)) | |
B4/6 | High-pressure fuel pressure sensor | Y74 | Pressure regulator valve | |
B5/1 | Boost pressure sensor | Y76 | Fuel injectors | |
B11/4 | Coolant temperature sensor | Y94 | Quantity control valve | |
B17/8 | Charge air temperature sensor | CAN E | Chassis CAN | |
B37/4 | Accelerator pedal module | CAN V | Vehicle CAN | |
B70 | Crankshaft Hall sensor | A | Mercedes-Benz | |
N3/28 | CDI control unit | B | Nissan | |
N30/4 | Electronic Stability Program (ESP) control unit | C | Default | |
N50 | Fuse and relay module control unit (SRM) | D | Optional | |
N93 | Central gateway (CGW) |
Function requirements for rpm control, general points
Circuit 87 (Engine management ON)
Engine running.
Rpm control, general
Rpm control stabilizes the idle speed and limits the engine speed to protect the engine and the drivetrain. The CDI control unit (N3/28) detects the engine speed via the crankshaft Hall sensor signal (B70).
For rpm limitation the CDI control unit reads in the following signals:
Crankshaft Hall sensor for engine speed
High pressure fuel pressure sensor (B4/6) for fuel pressure
Electronic Stability Program (ESP) control unit (N30/4) for vehicle speed
The engine speed is regulated by the CDI control unit by the following measures:
Actuation of the pressure regulating valve (Y74) (for fuel pressure control)
No actuation of the fuel injectors (Y76) (for rpm limitation)
Adaptation of the injection period of the fuel injectors (with idle speed control)
Actuation of the quantity control valve (Y94) (for fuel pressure control)
Function sequence for rpm control
Regulation of the engine speed is described in the following steps:
Function sequence for rpm limitation
Function sequence for idle speed control
Function sequence for rpm limitation
In order to protect the engine from the consequences of an impermissibly high engine speed while driving, the maximum engine speed is limited to approx. 4,500 rpm at a speed of > 0 km/h.
The CDI control unit detects the operating status is detected based on the "vehicle speed" CAN signal, which is transmitted by the Electronic Stability Program (ESP) control unit to the CDI control unit.
Function sequence for idle speed control
The CDI control unit regulates and stabilizes the idle speed depending on operating conditions and engine loads if the accelerator pedal is not actuated.
For idle speed control the CDI control unit also reads in the following signals:
Boost pressure sensor (B5/1) for engine load
Coolant temperature sensor (B11/4) for coolant temperature
Charge air temperature sensor (B17/8) for charge air temperature
Control unit for climate control (N154) for air conditioning status (with code H06 (air conditioning status) or with code HH4 (THERMOTRONIC automatic climate control))
The CDI control unit regulates the fuel pressure in the rail via the quantity control valve and the injection period via actuation of the fuel injectors.
The fuel pressure in the rail and the injection period of the fuel injectors determine the injection quantity. The idle speed can be raised for a limited time to approx. 1600 rpm depending on the atmospheric pressure and ambient temperature.
The CDI control unit regulates the idle speed in the following operating conditions and engine load conditions:
Switch-in of the A/C
On-board electrical system battery undervoltage (G1)
Switch-in of the A/C compressor with magnetic clutch
When the engine is in idle, so that the engine speed does not fall when the refrigerant compressor with magnetic clutch (A9/10) is switched in, the control unit for the climate control sends a status signal via the central gateway (CGW) (N93) to the CDI control unit before switching in. The CDI control unit adapts the idle speed appropriately.
If the following conditions exist, the CDI control unit quickly interrupts switching in the refrigerant compressor with magnetic clutch:
Starting off
Full open throttle request
Accelerator pedal module value (B37/4) > 95 %
The basic setting of the idle speed can be read out and influenced using the Xentry Diagnostics.
Undervoltage of the on-board electrical system battery
The CDI control unit recognizes undervoltage of the on-board electrical system battery via circuit 30 and increases the idle speed by approx. 100 rpm until the engine switches off.