Originally Posted by IMD

Hi. Sorry to hear that. By elsa to P0021 u have to do this to check if the "Camshaft Adjustment Valve 2 -N208" is working properly.for that u need multimeter to check the voltage and resistance. let me copy them and attach the pics

Camshaft Adjustment Valve, Checking

This procedure is used to check the Camshaft Adjustment Valves -N205 and N208-.
Special tools and workshop equipment required

t Multimeter -V.A.G 1526 A- or equivalent.
t Voltage Tester -VAG1527B- or equivalent.
t Adapter Cable (121-Point) -VAG1598/31-.
t Connector Test Set -VAG1594C-.

Test requirements
l Fuse for valve for camshaft adjustment OK. → Wiring diagrams, Troubleshooting & Component locations.
l Ignition switched off.
l The Fuel Pump (FP) Relay -J17- OK. → Chapter.

Note

Voltage for camshaft adjustment solenoid valves is supplied via the Motronic Engine Control Module (ECM) Power Supply Relay -J271-.
Test sequence

Cylinder bank 1 (right):
– Disconnect the electrical connector -2- from the Camshaft Adjustment Valve 1 -N205-.
A24-10017
Cylinder bank 2 (left):
– Remove the screw -arrow- retaining the coolant reservoir.
A10-1522
– Disconnect the electrical connector from Engine Coolant Level (ECL) Warning Switch -F66- at the bottom of the coolant reservoir and set aside the coolant reservoir with the coolant hoses -1- and -2- connected.
– Disconnect the electrical connector -3- from the Camshaft Adjustment Valve 2 -N208-.
A24-10046

Checking internal resistance

– Using the Multimeter -V.A.G 1526 A- or equivalent, check the following wiring connections for open circuit.
Specified value: 8 to 13 Ω.

If the specified value is not obtained:
– Replace the faulty Camshaft Adjustment Valve.
If specified value is obtained:

Checking voltage supply
A96-0342

– Using the Voltage Tester -VAG1527B- or equivalent, check the following wiring connection for voltage.

A24-0331
Harness connector
Terminal Measure to
1 Engine Ground (GND)

– Operate the starter briefly:
The LED must light up.
– Switch the ignition off.

If the LED does not light up:

– Check the wiring connection from terminal 1 of the electrical harness connector via fuse to the Motronic Engine Control Module (ECM) Power Supply Relay -J271- terminal 2 for an open circuit:
Specified value: Wire resistance max 1.5 Ω.
If the specified value is not obtained:
– Check the wiring for a short circuit to Battery positive (+) or an open circuit.
– If necessary, repair the wiring connection.
If the LED lights up.

Checking activation
– Connect the Adapter Cable (121-Point) -VAG1598/31- to the wiring harness of the Engine Control Module (ECM) -J623- ; the ECM is not connected. → Chapter.

– Using the Adapter Cable (121-Point) -VAG1598/31- and Multimeter -V.A.G 1526 A- or equivalent, check the following wiring connections for an open circuit.

l Camshaft Adjustment Valve 1 -N205- (bank 1).
A24-0331
Harness connector
Terminal Test box
Socket
2 115

l Camshaft Adjustment Valve 2 -N208- (bank 2).

Harness connector
Terminal Test box
Socket
2 120

If the specification is not obtained:

– Check the wiring for a short circuit to Battery positive (+) or an open circuit.
– If necessary, repair the wiring connection.
If no malfunctions are found in the wiring:
– Replace the Engine Control Module (ECM) -J623-. → Chapter.
If no malfunctions are detected:
– Replace mechanical camshaft adjuster. → Engine Mechanical; Rep. Gr.15.
Assembly is performed in the reverse order of removal, note the following:
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1 - Check the DTC memory. → Chapter.
2 - If necessary, erase the DTC memory. → Chapter.
3 - If the DTC memory was erased, generate readiness code. → Chapter.
– End diagnosis and switch the ignition off.

Originally Posted by Adam N.

Hi. Quick question if you dont mind. How do I get to n208 valve /selenoid on a 2004 s4 ? B6 4.2. Mine is stuck and I need to replace it, but have no idea how to get to it. Please help. Thank you in advance.