D32.33-A000-79
Level control block diagram |
A9/1 | Level control compressor | N97 | Electronic level control [ENR] control unit | |
A9/1m1 | Air compressor motor | N97k1 | ELC relay | |
A9/1y1 | Air compressor pressure relief valve | S77 | ELC switch (with code C2I (Air springs – switch in instrument panel)) | |
B22/9 | Left rear ELC level sensor | S77/1 | Level control switch (with code C2H (Air springs – switch in rear end)) | |
B22/10 | Right rear ELC level sensor | S78 | ELC remote control | |
H13/8 | Air spring warning buzzer | Y36 | Level control valve unit | |
N10 | SAM control unit | CAN B | Interior CAN | |
N26/15 | Parameterizable special module (PSM) control unit | O | Optional | |
N73/8 | Electronic ignition lock (EZS) control unit | S | Default |
Function requirement
No undervoltage
General
Electronic level control (ELC) is made possible by installing rear axle air suspension, which is a fully automatic 2-bag system. The air supply is provided by a maintenance-free, electrically-operated compressor with pressure reservoir and air drier. The compressor and pressure reservoir make it possible to quickly raise the vehicle (6 to 10 s with operating pressure in the pressure reservoir, up to 45 s with an empty pressure reservoir).
Function sequence for activation of level control
The ELC control unit is activated by switching on the ignition.
To do so, the electronic ignition lock (EZS) control unit sends the corresponding signal to the ELC control unit via the parameterizable special module (PSM) control unit. This actuates the level control compressor via the ELC relay.
After activation, the ELC control unit performs self-tests. If faults are detected, these are indicated by an acoustic signal from the air spring warning buzzer and by the corresponding indicator lamps in the ELC remote control lighting up.
To do this, the ELC control unit sends the corresponding request to the ELC remote control.
On vehicles with code C1N (Air suspension – run-on module 30 min), level control can be operated for up to 30 minutes after switching off the ignition. Voltage monitoring integrated into battery management prevents the on-board electrical system battery from excessive discharge.
The parameterizable special module (PSM) control unit receives the "On-board electrical system battery voltage" signal via the interior CAN and sends the corresponding signal to the ELC control unit.
Function sequence for actuation of level control (standard equipment)
The ELC control unit determines the current level using the ELC level sensors.
When the parking brake is released, level control is in automatic mode. If the current level deviates from the preset driving level, the ELC control unit actuates the level control compressor via the ELC relay until the driving level is reached.
When the parking brake is actuated, level control is in manual mode. The vehicle can be raised or lowered using the ELC remote control.
The parameterizable special module (PSM) control unit receives the "Parking brake position" signal via the interior CAN and sends the corresponding signal to the ELC control unit.
Function sequence for actuation of level control (with code C2A (Air springs, V-signal actuation))
As opposed to the standard equipment, swapping between manual mode and automatic mode here depends on the vehicle speed. The parking brake has no influence on actuation.
At a vehicle speed of 10 km/h, level control is in manual mode. Automatic mode is activated if 10 km/h is exceeded.
The parameterizable special module (PSM) control unit receives the "Vehicle speed" signal via the interior CAN and sends the corresponding signal to the ELC control unit.
Function sequence for actuation of level control (with code C2H (Air springs – switch in rear end))
In addition to the standard ELC remote control, the level control switch is installed on the D-pillar in the rear area.
The ELC control unit receives signals from the level control switch via a direct line.
Function sequence for actuation of level control (with code C2I (Air springs – switch in instrument panel))
In addition to the standard ELC remote control, the ELC switch is installed in the instrument panel.
The ELC control unit receives signals from the ELC switch via a direct line.
Height change
The vehicle can be raised by up to 40 mm by means of level control.
The vehicle can be lowered by up to 30 mm (without code CW2 (Discontinuation of vehicle lowering)) by means of level control.
The vehicle can be lowered by up to 45 mm (with code CW2 (Discontinuation of vehicle lowering)) by means of level control.
Manual deactivation of level control
Level control can be deactivated manually using the "SERVICE" button on the ELC remote control.
The ELC control unit receives signals from the ELC remote control via a direct line.
Automatic deactivation of level control
Level control is deactivated automatically under the following conditions:
If a fault was detected.
When engine is switched off and for undervoltage.
After repeated raising or lowering, so as to prevent the level control compressor overheating.
If the rear axle is raised quickly enough on one side or on both sides.
If the vehicle is on a vehicle lift for 80 s.
If the rear wheels have a level difference of more than 30 mm (curb detection).