From Ross-Tech Wiki

000175/P00AF - Actuator Module for Turbocharger 1: Stuck

Possible Symptoms

  • Malfunction Indicator Light (MIL) ON
  • Glow Plug light flashing
  • Reduced engine performance

Possible Causes

  • Defective N75
  • Vacuum leak or low vacuum
  • VNT sticking or seized
  • G581 sensor

Possible Solutions

  • Verify N75 is working to design, use Output Testing
  • Verify vacuum lines are good, check engine vacuum at idle
  • Test VNT and G581, apply vacuum to VNT and watch MVB 120.4
    • Engine off, no vacuum 120.4 should read about 3.5V
    • Engine Off, apply 17 Inches of mercury, 120.4 should drop to about .7V
    • Engine at idle, 120.4 should read about 7.V
    • If 120.4 voltage doesn't alter, VNT may be seized or G581 failed

Special Notes

  • On some TDI engines, the Vacuum Diaphragm/G581 unit can be purchased as a separate part from dealer.
  • 2.0L CR TDI owners may find this thread helpful: