Replacing heated oxygen sensors is a low-medium level DIY project you can do to save money on car repairs, and if your sensors are old, can increase your fuel economy.
Really straight foward to swap out. They should be done on a COLD car, i move it all of 10feet and running for 3 minutes and it was warm to the touch. Get yourself a Oxygen Sensor removal tool for the two top ones. Makes LIFE ALOT easier, if not you would have to do it the long way and remove the headshield surrounding the turbos (2hr job this way, ask me i know haha). Advice is to remove the sensors one at a time starting from the connector then goto the sensor, this way the wires dont get twisted all up.
I took out the air filter box to get to the two connectors for the front O2 sensors.
stick you hand in and follow the wires down. they clipped onto something on the transmission. pull them off the trans, the new sensors has new clips to put the connectors back onto the transmission. the white plug in the background is the front right sensor. the front left plug is black. they are keyed differently so there will not be any mix up and the rear is only a 4 pin plug.
You can mix up where to install the O2 sensors back in, take note on my 2003 T6 AWD car white is right, black on the left.
For the bottom sensor, i put my car up on ramps since it was time for the 2500 miles synthetic Mobile 1 Oil change
I used a open ended wrench for this one. It was a piece of cake, hardest part was getting enough leverage to get the sucker off, my car does have 152,000 miles
You will need a t15 torx to remove a clamp that holds the sensor wire in place. Expect yours to be rusted on like mine. I cut it off since old one was getting trashed anyways. I used a $0.50 1/2″ metal worm clamp to secure it to the exhaust hanger. Though about using a plastic ZIP tie but the potential heat issue kinda threw that idea out the window.
Here are what 152,000 mile O2 sensors look like. They seem pretty good, i really could not tell from the dis-assembly if they were changed before. they looked ok, but then again it might have been changed before. well now i know for sure they have been changed. I also did it in this order, bottom one first(had to change the oil too), then brought the car back down and did the top two sensors.
I changed the sensors in hope of getting better gas mileage. I have been averaging only 16.5mpg on the highway @65mph and 10-13 city. I know for sure though when my AWD was not working i averaged 21mpg coming home from a 350 mile road trip. I dont drive this car like i drive my convertible. I know I do not want to buy a new transmission, so she gets babied…the convertible gets DRIVEN
I will report back after a few tanks of gas to see if there was a change in miles per gallon. another note, it might be all in my head but, it does seem to idle smoother.
After MVS member changed all O2 sensors, his net gain in MPG was around 20%.
I plunged in and decided to try to change the front right sensor on my 2004 XC90. I bought a boch 17188 from www.sparkplugdepot.com/. It was the cheapest place I found that had international shipping.
I was able to get the sensor off with a fixed 22 mm spanner. I had to bend/hammer the aluminum headshield to get it on there. Fortunately the sensor isn’t heavily tightened. I included some pictures of it. I did remove the air filter box but it was really hard to get my hands on the wires, very tight. By pulling on the sensor wire I found it went far down and the only way for me to get it loose from where it was fixed with a clamp was from behind the front left tire. The clamp eventually broke off so I just left the new one hanging…”
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