Issue 4: The Air Supply System

The problem

When a diagnostic tool pointed to a common Air Mass Sensor fault it was thought that changing the part would instantly solve the problem. However upon further investigation it was found that other parts of the air supply system were to blame.

Vokswagen Touran Fault code P0100

The Investigation

  • The vehicle is experiencing poor acceleration and a loss of engine power, as shown on the stat sheet.
  • After using a diagnostic tool the fault code P0100 appeared, indicating an air flow circuit malfunction. This led to the Air Mass Sensor being replaced.
  • Once replaced, the warning light still appeared on the dashboard and the symptoms were still occurring.
  • On this particular model replacing the Air Mass Sensor may not always cure the fault.
  • After further investigation into the system, it was discovered that the Turbo Actuator was intermittently malfunctioning.
  • This caused the same symptoms that a faulty Air Mass Sensor would experience.
  • To rectify the situation the actuator must be replaced as the fault will become permanent over time.


  • As the VAG TDI engines rely heavily on the turbo at low-revs the part is more likely to become worn over time.
  • Checking that all Turbo air pipes are clean and free from any kinks & clogging will ensure the turbo isn’t put under any more pressure than needed.


Fault codes are only an indication of where the fault is occuring.Failure to check all aspects of the system can result in mis-diagnosis and high return rates!

Cambiare Tips and Tricks Issue 4 PDF