Use care when handling oxygen sensors as they are easily damaged by shock. To avoid possible engine damage, do not mix up oxygen sensor connectors; mark connectors before disassembling. Raise the vehicle and support it safely. Remove the front and rear engine lower covers, followed by the rear coil cover. While working at the rear of the engine, disconnect the oxygen sensor harness connectors, and if necessary, remove the fastener and connector bracket. Pre-catalyst wiring is grey, while post-catalyst wiring is black. Remove the post-catalyst oxygen sensor. For xDrive vehicles only, support the engine at the top and remove the right engine mount and engine support arm. Next, remove the exhaust system and the fasteners from the catalytic converter bracket, loosen the fastener, and release the clamp. When removing the exhaust clamp, ensure the catalytic converter is secured to prevent it from falling. Remove the catalytic converter from the bottom of the vehicle. Installation is the reverse of removal. NOTE-The exhaust clamp is single-use and must be replaced during reinstallation.