S07.10-0038-79
Block diagram |
A9/10 | Refrigerant compressor with magnetic clutch | N154 | Climate control control unit | |
B4/14 | Rail pressure sensor | S40/3 | Clutch pedal switch | |
B11/17 | Coolant temperature sensor | Y76 | Fuel injectors | |
B37/4 | Accelerator pedal module | Y94/3 | Quantity control valve | |
B70/2 | Crankshaft Hall sensor | CAN V | Vehicle CAN | |
N3/33 | CDI control unit | A | Mercedes-Benz | |
N10/1 | Signal acquisition and actuation module (SAM) control unit | B | Nissan | |
N30/4 | Electronic Stability Program (ESP) control unit | C | Default | |
N50 | Fuse and relay module control unit (SRM) | D | Option |
Function requirements for rpm control, general
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 (N3/33) detects the engine speed via the signal from the crankshaft Hall sensor (B70/2).
The CDI control unit (N3/33) governs the rpm control based, among others, on the following sensors and signals:
Rail pressure sensor (B4/14)
Coolant temperature sensor (B11/17)
Crankshaft Hall sensor (B70/2)
Wheel speed over the Electronic Stability Program control unit (ESP) (N30/4)
The engine speed is regulated by the CDI control unit (N3/33) by means of the following measures:
No actuation of the fuel injectors (Y76) (for rpm limitation)
Adaptation of the injection period
Actuation of quantity control valve (Y94/3)
Function sequence for rpm control, general
Regulation of the engine speed is described in the following steps:
Function sequence for the rpm limiter
Function sequence for idle speed control
Function sequence for the rpm limiter
During travel, the maximum engine speed is limited to 4500 rpm at speeds 0 km/h in order to protect the engine from the effects of inadmissibly high engine speeds.
Driving operation is recognized by the signal acquisition and actuation module (SAM) control unit (N10/1) based on the CAN signal "wheel speed" which is transmitted by the Electronic Stability Program (ESP) control unit (N30/4).
Function sequence for idle speed control
The CDI control unit (N3/33) regulates the idle speed depending on operating conditions and engine loads if the accelerator pedal is not operated.
To do this it reads in the following signals and others:
Status of air conditioning
Outside temperature
On-board power supply voltage
The CDI control unit (N3/33) uses the quantity control valve (Y94/3) to regulate the fuel quantity and therefore the fuel pressure in the rail and actuates the fuel injectors (Y76) to control the injection duration.
The fuel pressure in the rail and the injection period of the fuel injectors (Y76) determine the injection quantity.
The CDI control unit (N3/33) regulates the idle speed under the following operating and engine load conditions:
Actuation of the clutch pedal (for a manual transmission)
Switch-in of the A/C compressor with magnetic clutch
Undervoltage of the on-board electrical system battery
Actuation of the clutch pedal (for a manual transmission)
The CDI control unit (N3/33) recognizes actuation of the clutch pedal via the clutch pedal switch (S40/3) and regulates the engine rpm to obtain a stable idle speed.
Switch-in of the A/C compressor with magnetic clutch
To ensure in neutral that the engine rpm does not drop when the refrigerant compressor with magnetic clutch (A910) is engaged, the climate control control unit (N154) sends a status signal via the signal acquisition and actuation module (SAM) control unit (N10/1) to the CDI control unit (N3/33) before engagement. The CDI control unit(N3/33) appropriately adapts the idle speed.
When the following conditions are present, the CDI control unit (N3/33) shortly interrupts engagement of the refrigerant compressor with magnetic clutch (A9/10):
Starting off
Full open throttle request
Accelerator pedal module value (B37/4) > 95 %
Undervoltage of the on-board electrical system battery
The signal acquisition and actuation module (SAM) control unit (N10/1) recognizes an undervoltage of the on-board electrical system battery (G1) and increases the idle speed via the CDI control unit (N3/33).
Diagnosis
The basic setting of the idle speed can be read out and influenced using.