Scania Air Suspension Issues Explained

In this brief article we are going to discuss the different  Scania Air Suspension problems, what the causes are, and Troubleshooting Tips.

What are the most common  Scania Air suspension issues? 

The most common  Scania Air suspension issues are:

  • Suspension Calibration Error
  • Air Spring Leakage
  • Suspension Rising and Falling
  • Moisture in the sensors

Scania Air Suspension Set-up

The Scania Air Suspension for the 6X2 is a system of 4 corner air springs at the 2 rear axles with a provision to lift the forward rear axle when there is no trailer hitched to the truck.

The lower control arms of each corner is actually a leafspring. Hence, the spring rate at each corner is a combined effect of the leafspring deflection and the air spring compression. This sort of system is highly beneficial to ride quality since the effective rate of 2 springs acting in series is a lower stiffness.

Suspension calibration Error

  • After performing the calibration on all levels there is an error

SMS 642

  • Diagnostics does not read all suspension sensors
  • It is possible that the proper ride height values were not entered when doing the calibration setup in the diagnostic tool
  • As per the diagnostic software, the difference between normal and low level cannot be less than 40 mm since the software might reject the inputs you keyed in while doing the calibration, 
  • Between normal and low levels of ride height, the difference should be below 60 mm.
  • Air springs must be lifted by at least 60 mm. from the “empty” level. 
  • Setting the ride height difference to less than 60mm, will result in often mechanical suspension failures. With a lesser difference, the air spring will not be effective, and so the other suspension parts will share the distributed truck weight. This will be particularly harmful when the truck goes over bumps.

Air spring leakage

  • After starting the truck, a continuous “Hissing” noise is heard
  • Ride Height Lower than Normal
  • Bad Ride quality due to hitting the bump stops often

The suspension height falls after Rising

  • The Solenoid valve that controls the raising / lowering of the suspension height (by means of filling or bleeding air from the Air springs) has stuck.
  • This means that the solenoid valve is constantly activated due to the required vehicle position height not being achieved.

Moisture penetrating sensors

  • Moisture penetrating the pressure sensors can cause incorrect load distribution between the 2 rear axles 
  • Since the control unit will not be able to read the sensor signal, the suspension height cannot be adjusted either manually or automatically.

Diagnostic mode

  • Fault codes that have been stored by the suspension control unit can be read out using the OE-recommended diagnostic tool.
  • Fault codes can also be read using the diagnostic lamp that Scania provides.

Conclusion

In this brief article we have discussed the different  Scania Air Suspension problems, what the causes are, and Troubleshooting Tips.

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