Exhaust Flap (E65, N62 up to 09/2003)

The exhaust flap is fitted on the exhaust tailpipe and it serves to reduce noise at idle speed and the engine speed range close to idling.

Function

• The exhaust flap is held in the ”open” position by spring force. When the engine is off, this means the exhaust flap is always open.
  
• The exhaust flap is closed by means of a diaphragm can with partial vacuum.
  
• The diaphragm can is activated via a solenoid valve (Y198). Activation is controlled by a map via the DME.
  
• When the engine is switched off, the diaphragm can is vented via a throttle so that the exhaust flap is damped as it opens. The change over to the throttle takes place via a second solenoid valve (Y0198). An electrical fault of the 2nd solenoid valve is not detected by the DME.
  

Causes

The control unit only detects electrical faults. In the case of a fault entry, the following causes are possible:

• Wiring harness defective
  
• Solenoid valve (Y198) defective
  
• DME defective
  

If the components are activated and the exhaust flap does not react or only reacts inadequately, the following causes are possible:

• Vacuum supply leaking or defective
  
• Exhaust flap mechanically defective
  

Note: When the exhaust flap is closed continuously, a hiss can be heard at high load and engine speed. If the exhaust flap is open continuously, a hum can be heard at idle speed.

If the 2nd solenoid valve (Y0198) is defective, the exhaust flap can be heard to open when the engine is stopped.