S8 Quattro Sedan V8-4.2L (AYS) (2002)
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Connect VAG1527B voltage tester to connector socket 1 and engine Ground (GND) using adapter cables from VAG1594 connector test kit.
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Operate starter briefly.
LED must light up.
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LED does not light up.
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Check fuse for intake manifold change-over valve.
Voltage supply is OK.
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Wire connection from connector socket 1 via fuse for intake manifold change-over valve to fuel pump relay for open circuit or short circuit.
If the voltage supply is OK, check activation.
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Re-install fuel pump relay and fuse.
Checking activation of intake manifold change-over valve
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Connect VAG1527B voltage tester using cables from VAG1594 connector test kit to sockets 1 (B+) and 2 of connector to intake manifold
change-over valve.
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Perform output Diagnostic Test Mode (DTM) and activate the respective intake manifold change-over valve. Refer to Scan Tool Testing/Output
Diagnostic Test Mode (DTM) (Function 03) See: Computers and Control Systems/Testing and Inspection
Indicated on display:
Output Diagnostic Test Mode (DTM) ->
Intake manifold change-over valve -N156
If LED does not blink or if it remains constantly lit. Check wire connection.
Checking wire connection
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Connect VAG1598/31 test box at wiring harness to Engine Control Module (ECM), do not connect ECM. Refer to "Scan Tool Testing/Scan Tool
Connecting and Initial Checks/Connecting VAG1598/31 Test Box" See: Computers and Control Systems/Testing and Inspection