2 Check wiring harness for short to B+.
1. Remove connector of change-over valve.
2. Connect voltmeter to connector, pin 2 (positive), and ground (negative). Switch on the ignition.
Display: 0 V
If battery voltage is displayed, check wiring harness for chafing and pinching damage.
3 Perform adaptation.
1. Switch on the ignition.
2. Wait one minute.
Do not press the accelerator.
3. Switch off the ignition for at least 10 seconds.
4. Read out the fault memory.
4 Check wiring harness for short to ground.
1. Remove connector of change-over valve.
2. Connect ohmmeter to connector, pin 2, and ground.
Display: infinity ohms
If 0 - 5 ohms is displayed, check wiring harness for chafing and pinching damage.
5 Check wiring harness for open circuit.
1. Connect special tool 9637 to wiring harness (DME control module connector).
2. Remove connector of change-over valve.
3. Connect ohmmeter to special tool 9637, pin III/4, and change-over valve connector, pin 2.
Display: 0 - 5 ohms
NOTE: The wire is routed via connector X 59/1, pin 10. If infinity ohms is displayed, check connector X59/1, pin 10, for corrosion, and check
wiring harness for chafing and pinching damage.
Electric Change-Over Valve, Variable-Length Manifold (Output Stage) - Below Limit
P1670
Electric Change-over Valve, Variable-Length Manifold (Output Stage) - Below Limit
Function
An intake air system divided by a tuning flap permits the oscillations of the intake air column to be exploited over a large engine speed range
(resonance supercharging).
During this process, the different power strokes of the individual cylinders mean that air is sucked up from both reservoirs of the intake air system in
alternation. This alternating suction excites the air mass in the intake air system. During resonance, the intake frequency of a cylinder bank
corresponds with the natural frequency of compressive oscillations in the associated reservoir. The natural frequency is determined by the geometry
of the intake manifolds, resonance pipes and reservoirs. A decisive factor, however, is the overall length of the pipes from one intake cylinder to the
next, the different lengths of intake and resonance pipe sections and the depth of the reservoir in the direction of flow.
The DME control module activates a change-over valve which opens and shuts the tuning flap through vacuum. The tuning flap is open without
flow, but is actuated and closed each time the ignition is switched on. Once the engine reaches the programmed idle speed after start-up, the tuning
flap is opened once more.
Switching points of the tuning flap:
Tuning flap actuated from 2720 to 5160 rpm when speed is increasing or from 5080 to 2640 rpm when speed is decreasing, if the throttle is also
more than 15 % open at the same time.
Diagnosis conditions
- Intake air temperature > 30 锟斤拷C
- Engine temperature > 20 锟斤拷C