Testing turbo VNT actuator position sensor?

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Joined: 30 Nov 2021, 10:12

Testing turbo VNT actuator position sensor?

Post by yason »

After some VNT trouble last year I have the turbo off my DS5 hdi163 (RHH) on the bench for cleaning the VNT vanes. While I'm at it I'd like to test the VNT actuator position sensor as well but it seems I don't seem to get anything sensible out of the three pins.

Does anyone know how to test the position sensor that sits on top of the actuator? I assume it has a potentiometer or hall effect position sensor inside but I wonder if the three pins correspond to those directly? Or if there's something else that's required? My understanding is that given a reference voltage the signal voltage will then vary depending on the rod position.

I've seen P2563 which is turbo VNT position difference between copied and requested. This is fine if it was the vanes that got stuck for a while but it's also possible the position reading was bad. The position reading is what I'd like to test now that I have access.

Sedre gives me the following details for the wires:
  • 1419A: sensor supply
    1420A: sensor earth
    1421A: sensor signal
Using a bench power supply and an oscilloscope I fed +5V to supply, connected earth to earth and set up my scope between the signal wire and earth. I get a steady voltage of about 0.9V on the signal wire but that does not change when I supply vacuum to pull the actuator rod back and forth between the shortest and longest positions.

If the pins do correspond to the internal sensor component directly then I'd say the actuator sensor is shot. But I'm not sure of the correct test procedure and if anyone knows more about this, please share. I'd like to get some confirmation one way or another before I buy a new actuator unit.