We are going to diagnose and repair a fault that affects Audi Q7 models (4L) manufactured from 2007.
These models are equipped with Adaptive Air Suspension (AAS) self-levelling suspension system.
The diagnostic fault codes recorded in the Level Control Unit (J197) are:
- Code 1781 - Extreme inclination of the vehicle, maximum threshold value exceeded
The vehicle is unstable and wanders on the road and remains inclined to one side and the reference ride height position cannot be activated and/or adjusted on the menu on the Multi-Media Interface (MMI) screen within the vehicle.
The cause of this fault is due to an internal defect in the residual pressure check valve for the pneumatic spring/damper assembly.
The repair procedure involves placing the vehicle on the top suspension level setting, this is accessed by selecting CAR and SETUP through the Multi-Media Interface (MMI) menu screen.
Then raise the vehicle on a suitable workshop lift and remove the plastic protector panel from the right foot-step to gain access to the compressor and the valve unit assembly.
You will now see the four air pipes in the valve unit that correspond to each pneumatic air damper: slowly slacken each pipe taking care not to injure yourself or the vehicle.
Identify which pipe is not allowing the air to escape and note the pipe colour and replace the residual pressure check valve of the corresponding pneumatic spring/damper assembly of the pipe that is not releasing the air when the pipe is slackened off.
NOTE: Before replacing the residual pressure check valve for the spring/damper assembly, place the vehicle in "Vehicle Lift Mode".
The Vehicle Lift Mode is accessed through the Multi-Media Interface Unit (MMI) inside the vehicle and to activate/deactivate the system you are required to follow the these procedures
A - Valve unit.
B – Black pipe: solenoid valve and internal compressor.
C - Green pipe: air supply for the right front pneumatic damper.
D - Red pipe: air supply for the left rear pneumatic damper.
E - Violet pipe: air supply for the left front pneumatic damper.
F - Blue pipe: air supply for the accumulators.
G - Yellow pipe: air supply for the right rear pneumatic damper.