Originally Posted by drjekl
Has anyone got a diy with pics preferably for the N54, and are the 02 sensor specific wrenches/sockets worth purchasing or are these more of a 'nice' to have item?
There are pictures of how to remove the engine cover in other DIYs (for spark plugs and fuel injectors) but the procedure for the N54 is pretty much the same as for the N52. The O2 sensor harnesses for the two pre-cat sensors go underneath the engine cover and are routed in channels and harness clips that require removal of the engine cover. The post-cat sensors do not need the engine cover removed.
You can use a 7/8ths box wrench on the sensor if you can fit one on it, but you have to cut the cable off; the connector does not fit through the wrench opening. I don't think a 7/8 deep socket will fit over the O2 sensor even with the cable completely removed. The special sockets are not that expensive and every auto parts store will have the correct sized socket.