I know that replacing the oxygen sensors is one of the simpler fixes to save a few bucks. Here’s my experience if it helps anyone.
I’ve got a 2003 LX470. I had a check engine light with a P0031 code indicating a bad O2 sensor (upstream, driver’s side). Also, both of the VSC lights were on (VSC Trac and VSC Off), but some research on this site indicated that it was probably related to the O2 sensor and would clear if I replaced it.
Per best practice, I replaced both upstream sensors, driver’s side and passenger side. Denso 234-4138 from Rock Auto, about $100 delivered. Here are some tools and tips you may find useful.
Prep
I drove the front end up on ramps and removed both the skid plate and the plastic shroud (12 mm bolts). For the sensors alone the plastic shroud probably would have been enough but I was also replacing the oil pressure sending unit. Found both upstream sensors and sprayed some Liquid Wrench around the connections. Let the truck run enough to get a little warm but not hot. Ate lunch.
The Tool
I purchased a 7/8” O2 sensor removal socket at NAPA. It has a half-inch drive (for a socket wrench) and also a one inch wrench end. Worth every penny.
Driver Side
On the driver’s side, there is interference which makes it impossible to use a half-inch socket wrench and tricky to use the 1” wrench end on the removal socket. See arrow, below:
To loosen this side, I put the O2 socket on the sensor, and then used a large adjustable wrench around the body of the socket. I didn’t have enough hands to take a picture under the truck, but here’s the idea:
When I did this job previously on my 2001 LX, the driver’s side was really hard to loosen. I ended up using a cheater bar to get more leverage (basically a 2-inch square pipe over the end of the adjustable wrench).
Passenger Side
I’ve read that some people remove the RF wheel and fender liner to access this sensor, but I actually found this one easier to remove than the driver’s side sensor from under the truck. Here’s the view from below:
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I’ve got a 2003 LX470. I had a check engine light with a P0031 code indicating a bad O2 sensor (upstream, driver’s side). Also, both of the VSC lights were on (VSC Trac and VSC Off), but some research on this site indicated that it was probably related to the O2 sensor and would clear if I replaced it.
Per best practice, I replaced both upstream sensors, driver’s side and passenger side. Denso 234-4138 from Rock Auto, about $100 delivered. Here are some tools and tips you may find useful.
Prep
I drove the front end up on ramps and removed both the skid plate and the plastic shroud (12 mm bolts). For the sensors alone the plastic shroud probably would have been enough but I was also replacing the oil pressure sending unit. Found both upstream sensors and sprayed some Liquid Wrench around the connections. Let the truck run enough to get a little warm but not hot. Ate lunch.
The Tool
I purchased a 7/8” O2 sensor removal socket at NAPA. It has a half-inch drive (for a socket wrench) and also a one inch wrench end. Worth every penny.
Driver Side
On the driver’s side, there is interference which makes it impossible to use a half-inch socket wrench and tricky to use the 1” wrench end on the removal socket. See arrow, below:
To loosen this side, I put the O2 socket on the sensor, and then used a large adjustable wrench around the body of the socket. I didn’t have enough hands to take a picture under the truck, but here’s the idea:
When I did this job previously on my 2001 LX, the driver’s side was really hard to loosen. I ended up using a cheater bar to get more leverage (basically a 2-inch square pipe over the end of the adjustable wrench).
Passenger Side
I’ve read that some people remove the RF wheel and fender liner to access this sensor, but I actually found this one easier to remove than the driver’s side sensor from under the truck. Here’s the view from below:
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