1997-2001 Q45 O2 Sensor Replacement

Y33 O2 Sensor Replacement

By:bullittandy

Just finished the O2 sensors (all 4) on my 97 Q45. Here’s a heads up for others attempting the job.

WD-40 / PB Blaster MUST be used! Don’t try to do anything until the sensor nuts have soaked for at least 30 minutes but the longer the better (I soaked them the night before).

The rears are easy.However, I got a little nervous about the fronts when I had to use my mini sledge hammer in order to break the rears free.

The front passenger side has been discussed in previous posts-same applies here.Using a O2 socket (crows-foot style, rented from Autozone) from the bottom of the car slip it over the sensor. Then from the top of the car in the engine bay drop a long extension into the sensor socket. I used a flex joint to get a better angle.

The front driver side was the fun one!I had trouble reaching it from any angle – top, bottom, anywhere.So I removed the master cylinder and brake booster.Do not remove the brake lines from the M/C just unbolt it from the booster and move out of the way. The length of the brake lines allows it to be moved easily.

The brake booster was a little more difficult. It is held on by 4 bolts inside the car, 2 of which are easily seen, 1 is somewhat tricky and the 4th nut (upper right from driver’s seat) was very difficult.Find access any way you can.Putting this nut back on required me to tape the nut to the end of my finger!With this I was able to get it on the brake booster stud the second try.

Overall this was harder than replacing the knock sensors. But, the gas mileage increase will be worth all the pain and frustration!!