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Testing auxiliary signals > < Inspect the vacuum system

Octavia Mk1

Test variable intake manifold changeover valve N156
Test variable intake manifold changeover valve -N156-
Fitting location → Chapter.
Special tools and workshop equipment required
t  Handheld multimeter, e.g. -V.A.G 1526 A -
t  Voltage tester, e.°g. - V.A.G 1527-
t  Measuring tool set, e.g. -V.A.G 1594 A-
t  Test box, e.g. -V.A.G 1598/22 -
Test condition
l  Fuse 34 must be OK.
Electrically test valve for variable intake manifold changeover -N156-
–  Disconnect plug at variable intake manifold changeover valve.
–  Measure the resistance between the contacts of the variable intake manifold changeover valve.
   
Specified value: 25 to 35 Ω.
If the specified value is not reached, replace the variable intake manifold changeover valve.
Test voltage supply and actuation of the variable intake manifold changeover valve -N156-
  S24-0216
–  Disconnect plug at variable intake manifold changeover valve.
–  Connect the voltage tester to contact 1 (positive) of the plug and to the engine mass.
–  Switch on the starter motor for a short time. While doing so, the engine can also start. Specified value: The voltage tester must light up.
The diode does not light up:
–  Check the cable of contact 1 of the plug at the variable intake manifold changeover valve to fuse for continuity according to the current flow diagram → Current flow diagrams and Fitting locations.
–  If the fuse and the wiring are o.k, check the actuation of the fuel pump relay → Chapter.
  S24-0217
–  Connect voltage tester to contact 1 (positive) and 2 (actuation of engine control unit) of the plug at the variable intake manifold changeover valve.
–  Initiating final control diagnosis → Chapter.
The voltage tester must flash for the actuation of the valve for variable intake manifold changeover.
–  If the voltage tester does not flash or if it remains lit. Connect the test box -V.A.G 1598/22- to the wiring loom of the engine control unit → Chapter.
–  If the voltage tester lights up continuously, test the wiring of contact 2 of the plug for variable intake manifold changeover valve to socket 64 of the test box for short circuit to earth.
–  If the voltage tester does not flash, test the wiring of contact 2 of the plug at the variable intake manifold changeover valve to socket 64 of the test box for short circuit to positive.
–  If necessary eliminate fault.
–  If there is neither a line interruption nor a short-circuit; replace engine control unit → Chapter.
  S24-0218

Testing auxiliary signals > < Inspect the vacuum system