Checking solenoid valve for boost pressure control: Audi 1.8 (AGU)
Step-by-step checking solenoid valve for boost pressure control for the Audi 1.8 (AGU): factory workshop text.
Workshop procedure for AUDI — the factory write-up, straight from real workshop data.
🔧 Engine codes this applies to
📋 Procedure
Checking operation
Pull the hoses off the -N75 solenoid valve for boost pressure control
=> Fitting locations -Overview - Page
24-5
.
Connect auxiliary hose.
Start the final control diagnosis and actuate the -N75 solenoid valve for boost pressure control =>Page
01-46
.
Final control diagnosis
⇒
-N75 solenoid valve for boost pressure control
Display readout:
The valve should click...
...and should open and close (check by blowing into the auxiliary hose).
If the valve does not click:
Check the solenoid valve for boost pressure control electrically => Page
24-37
.
When there is no electrical signal, the long connection is closed.
If the solenoid valve clicks, but does not open and close properly:
Replace the solenoid valve for boost pressure control (N75).
Electrical check on solenoid valve for boost pressure control (N75).
Unplug the connector from the valve
=> Fitting locations - Overview - Page
24-5
.
Connect the V.A.G 1526 hand held multimeter for resistance measurement to the valve.
Specified value: 25...35 ω.
If the specified value is not achieved:
Replace the solenoid valve for boost pressure control (N75).
If the specified value is achieved:
Check the power supply from the solenoid valve for boost pressure control => Page
24-38
.
Check the power supply to the solenoid valve for boost pressure control (N75).
Connect the V.A.G 1526 hand held multimeter for voltage measurement to contact 1 of the connector and the earth.
Operate the starter briefly (the engine may start briefly).
Specified value: approx. battery voltage.
If the specified value is not achieved:
Check the wiring from contact 1 on the connector via the fuse to the fuel pump relay for an open circuit or short circuit.
=> Current Flow Diagrams, Electrical Fault Finding and Fitting Locations binder
If the specified value is achieved:
Check the actuation for the solenoid valve for boost pressure control => Page
24-39
.
Checking the actuation of the solenoid valve for the boost pressure control (N75)
Unplug the connector from the solenoid valve (N75) and connect the V.A.G 1527 diode test lamp between connector contacts 1 and 2.
Start the final control diagnosis and actuate the N75 solenoid valve for boost pressure control =>Page
01-46
.
The diode test lamp should start flashing.
If diode test lamp does not flash or if the lamp is lit continuously. Check the wiring.
Connect the V.A.G 1598/22 test box to the wiring harness for the engine control unit
=>Page
24-8
.
The following wiring should be checked for a short to positive or negative and an open circuit:
2-pin connector on the wiring harness contact. · Test box V.A.G 1598/22 contact.
2 · 64
If necessary, rectify open circuit or short circuit.
TorqFix answers live for your specific car — tell it the engine code and it serves the matching sequence, torque figures and wiring for that exact variant.
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Who makes these pages, and how
TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.
The figures on this page come from manufacturer workshop documentation and are shown as they are. The page is assembled automatically from that data — it is not written by an AI. The AI works in the chat, where it answers for your specific car. It writes nothing here.
Variants of the same model differ. Cross-check torque against the factory manual for your engine before final tightening.
Seen a figure that does not match your manual? Write to us — we correct it and note when. support@torqfix.com
The story behind TorqFix →Workshop data on this page last updated 20 Sep 2026.