With the engine off, check by hand to see if the throttle actuator rod is jammed. If the stem is stuck, replace the turbocharger.
At idle, while operating the boost pressure control solenoid valve with SCR = 85%, disconnect the solenoid valve wire connector while observing whether the boost pressure control damper actuator stem moves. If the boost pressure control damper rod moves from lock to lock, the boost pressure control control circuit is working properly.
If not, check the condition of the boost pressure control solenoid valve connector (there are no signs of oxidation, bent pins, etc.). Check the resistance of the boost pressure control solenoid between tracks 1 and 2. It should be within:
- 15.4 Ohm±0.7 Ohm at + 20°С for Pierburg solenoid valve;
- 16.5 ohm±1.6 ohm at + 25°C, for Bitron solenoid valve.
If the solenoid valve is defective, replace it.
If the solenoid valve is OK, check for open and short to +12 V and to «mass» wires in the circuit between track L2 of connector B of the injection computer and track 1 of the boost pressure control solenoid valve connector. Check the absence of breaks and short circuits on «ground* of the wires in the circuit between the 12 V circuit after the injection system relay and track 2 of the boost pressure control solenoid valve connector.
Connect the boost pressure control solenoid valve connector. Disconnect the hose coming from the solenoid valve from the pneumatic actuator. Attach a pressure gauge instead, with the engine idling.
If the vacuum at the outlet of the hose is greater than 750 mbar. check the boost pressure regulator flap.
Check the tightness of the damper on the seat in the extreme position.
Make sure the damper is at the stop at the maximum control signal.
Check the ease of movement of the actuator stem for the entire stroke.
If the problem persists, replace the turbocharger.
If the vacuum at the outlet of the hose is less than 750 mbar, check the vacuum at the inlet of the boost pressure control solenoid valve.
If the value is greater than 750 mbar, replace the boost pressure control solenoid valve.
If the value does not exceed 750 mbar, check the vacuum circuit and repeat the test, starting with checking the vacuum value.