Variable Induction Control Valve: Testing and Inspection

Intake Manifold Tuning (IMT) valve, checking

NOTE:
- Carry out this check for complaints of poor performance only.
- The tuning (change-over) of the manifold from long to short intake path occurs at approx. 4500 RPM.

Special tools and equipment
- VAG1551 or VAG1552 Scan Tool (ST) with VAG1551/3 adapter cable
- VAG1598/22 test box
- Multimeter US1119 (Fluke 83 or equivalent)
- VW1594 connector test kit
- VAG1527B LED voltage tester
- VAG1390 hand pump
- Wiring diagrams

Check requirements





- Fuse 29 OK
- Fuel pump relay OK


Checking function
- Start engine and run at idle.
- Increase engine RPM clearly above 4500 RPM.
Intake manifold tuning vacuum solenoid must be actuated (solenoid is located on intake manifold, left-front, under the ignition coils).

If the vacuum solenoid is not actuated:
- Conduct output Diagnostic Test Mode (DTM) for Intake Manifold Tuning (IMT) valve -N156-. [1][2][3]Output Diagnostic Test Mode (DTM) (Function 03)

If actuation is OK:
- Leave scan tool connected.






- Disconnect vacuum hose -1- from one- way valve -2- and connect VAG1390 hand pump to disconnected hose.
- Conduct output Diagnostic Test Mode (DTM) again. When Intake Manifold Tuning (IMT) valve -N156-is actuated, operate hand pump.






The actuator must switch (change-over) between open and close (arrow).

If the change-over does not function as described:
- Check change-over mechanics for freedom of movement. To do this operate rods by hand.
- Check vacuum hoses for correct routing.
- Check vacuum system including vacuum reservoir in left wheel housing for leaks.

Electrical check of intake manifold tuning valve -N156-






- Disconnect harness connector -1- from Intake Manifold Tuning (IMT) valve -2-.






- Connect multimeter between terminals of IMT valve and measure resistance.
Specified value: 25-35 Ohms.

If the specified value is not attained:
- Replace Intake Manifold Tuning (IMT) valve.
- Check readiness code. If Diagnostic Trouble Code (DTC) memory has been erased, or ECM was disconnected, generate new readiness code. Monitors, Trips, Drive Cycles and Readiness Codes