40" O2 Oxygen Sensor 4 Wire Extension Harness for VW Audi Golf MK7 Passat If you are installing an aftermarket downpipe(s) on your Volkswagen or Audi you may need to install your post catalytic converter oxygen sensors further away from the engine. This secondary oxygen sensor extension is 40” long and easily connects between the oxygen sensor and the car's wiring harness allowing the oxygen sensor to be installed further down on a downpipe(s). Please note 4.0T engines require 2 harness extensions.