Check Oxygen Sensor

Heat the oxygen sensors (road test car under load or run engine without load at high RPM).
Connect Porsche System Tester 2 or scan tool and read voltage of oxygen sensor 2 ahead of TWC.
Display: Voltage fluctuations between 0 mV and 800 mV.

Oxygen sensor OK.

If a value around 0V is displayed, a short circuit has occurred between the signal wire and sensor ground.

If a value between 100 mV and 300 mV is displayed, limited voltage increase is present.

If a value between 550 mV and 1,500 mV is displayed, a short circuit to battery positive voltage is present.
Remove oxygen sensor connector 2 ahead of TWC.
Connect voltmeter to pins 3 and 4 of connector to DME control module.
Display: approx. 450 mV

Replace oxygen sensor.

Display: < 400 mV or > 500 mV

Check wiring harness.