MVS Forums contributor deepsouth shows us how a front O2 sensor swap is done on an AWD Volvo P80, including photos. This is a “from the top” DIY, meaning it’s how to do the front sensor swap access from the engine bay, not under the car. Outstanding.
Just swapped the front O2 sensor on my 1998 Volvo V70 AWD and documented it for those interested. On the AWD the sensor must be swapped from the top and it’s a bit of a bear to reach. Here are the steps.
1. Disconnect negative cable from battery.
2. Remove MAF sensor connection, smog pump hose, and upper hose clamp from turbo air pipe (see photos).
3. Remove air box from engine compartment.
4. Disconnect vacuum lines from upper half of turbo air pipe (2 lines, one on side and underneath) and from lower pipe at PTC Nipple (3 vacuum lines and an electrical connector…see photos).
5. Remove hose clamp that holds turbo air pipe to turbo. This is largely a “by feel” clamp and is difficult to see (see photo).
6. Remove turbo air pipe.
7. The upper and lower O2 sensor connectors are now visible. The red tab is a locking mechanism and must be slid out before connector can be removed.
8. Using crow’s foot O2 wrench (for rent at any parts store), u-joint, and long extension (or many small ones pieced together ) break loose old O2 sensor. This step is not fun nor easy and there is very little clearance.
9. The new sensor is a PITA to thread and install as well. I wound the wire the opposite direction several times before attempting to thread.
10. Tighten new sensor with crow’s foot and reassemble. It’s also a good time to clean and inspect PTC nipple.