Rear axle level control system control unit, task - GF32.33-P-3300-01A

The rear axle level control system control unit (N97) has the following tasks: 

Read in the following discrete signals 

• Rear axle level sensor (B22/3)
• Wake-up signal
• Circuit 30
• Circuit 31
• Circuit 87

Read in the following CAN class C messages 

• Vehicle speed
• Steering wheel angle
• Outside air temperature
• Air pressure
• Door status
• Transmitter key (A8/1) status

Actuation 

• AIRmatic compressor unit (A9/1)
• Drain valve for AIRmatic compressor unit (A9/1)
• AIRmatic relay (K67)
• Left rear level control valve (Y36/3)
• Right rear level control valve (Y36/4)

Lock position 

If the rear axle level control system control unit (N97) detects that the rear wheels have been unloaded when the vehicle is stationary, the left rear level control valve (Y36/3) and the right rear level control valve (Y36/4) are closed. The vehicle therefore remains at the current level. This is essential, for example, when changing a wheel or during repair work (lifting platform).

Safety circuit 

After switching on and during operation the rear axle level control system control unit (N97) monitors all the important components of the electronic rear axle level control system. The safety circuit detects faulty signals from sensors, faults in the rear axle level control system control unit (N97) and in the electric line system. If a fault is detected, the system is switched off only partially according (A1) to the particular fault and this is indicated to the driver by means of the multifunction display (A1p13) in the instrument cluster.

A fault code is also stored in the rear axle level control system control unit (N97). The system always strives to maintain the selected vehicle level.

The safety circuit also constantly monitors the battery voltage. If the voltage drops below 9.0 V or rises above 16.5 V, the system is likewise switched off until the voltage is again within the specified range.