whitels

I just replaced the two front oxygen sensors and I've got to tell you that the car is definitely more responsive to throttle action as compared to how the SC drove for years before that!!! It reminded me of my previous GS400 which I had before the SC - responsive, responsive, responsive. Fuel economy is up. Where I used to see 21.4MPG average before "tops" on my information display, I'm seeing 23.5 now. This is for the same 52-mile round trip commute that I do everyday for years!!!.

My understanding is sometime in 2004, Denso stopped manufacturing the original factory installed oxygen sensors for the 3UZ engine family, 89465-50120 (left front) and 89465-50130 (right front). It came out with a revision.

Because of a recent check engine light, I found that my original left side sensor is bad and decided to replace both with new Denso universal 4-wire part number 234-4209. Bought two pieces from Amazon http://www.amazon.com/Denso-2344209-...0149318&sr=8-1 for about $80 shipped.

I chose Denso universal because it seemed easier for me to just cut and splice/solder the wires. It's just a matter of matching the wire colors: black to black (two of these), blue to blue, and white to white. Unsnapping the factory connectors is a royal pain. On the right side, I can't even find the connector! And the best part is you can buy TWO pieces of Denso universal sensors for under the cost of one Denso sensor with connector! Its the same sensor anyway.

The only thing to really watch out for is it seems far too common to have the sensor thread get stripped when removing the original sensor. In my case, the left side came out with no problem. The right side stripped. The fix is to buy an 18mm oxygen sensor thread chaser for $8 from an auto part store. And when you start the thread chaser, make sure it is squarely flat against the sensor hole/bung or the sensor will not seat squarely and might cause a small exhaust leak and therefore some noise and smog emission issues with manifold leak. I learned (after I stripped mine, of course) that stripping might be avoided if you remove the sensor when the exhaust pipe is hot (120 degree or more). Others spray penetrating oil or liquid wrench 24 hours before.

AspenSC

Whiltels: What year is your SC430?

whitels

2002 model year

Harold57

I noticed an increase in mileage on my '02 also when the oxygen sensor was replaced about a year ago. (Mine was covered under warrantee. I got lucky there.)

I8ABMR

i can imagine that this would be the case. Thats really cool. Better response and gas mileage and it probably didnt break the bank

whitels

A CL member asked me if maybe the sensors should be replaced in pairs, like computer memory. In his case, his mileage dropped after one of the front sensors was replaced by a dealer. It was replaced twice to make sure that the new sensor was not the offending part. It still did not fix the mileage drop.

This is what I'm thinking. I don't think sensors need to be replaced in pairs. And here's why. As soon as I replaced the bad one with a new updated sensor on my SC (leaving the old sensor on the other side still installed), I drove the car for a day-- about 60 miles total-- and found that I had better mileage right away. My MPG info broke through the historical ceiling of 21.4MPG average.

I don't have enough data to say that had I kept both the old and new sensors installed that it would give the same mileage as having two new sensors in there.

The only reason I replaced the other one is because I think it's next in line to fail soon and I'm lazy to to get and put away my tools two times ;-)

That being said, it also reminded me of my GS400. Sensors are funny in that it could already be bad and it's not throwing off any codes. It took Longo Lexus three times (two techs and finally to the supervisor) to diagnose a bad sensor in my GS. The symptoms were bad mileage and uneven idling or somewhat unsteady idling. If you have those symptoms, then I suspect the other sensor has gone bad. I know it's hard to believe that two sensors would go bad at the same time -- it's highly improbable.

IcEnPinKi

iTrader: (1)

I need to replace my O2 sensors as well..driver side and passenger side...Did you change the sensors yourself? Dealer list around $170.00 for the sensors... Is there any plug and play versions? The connectors are under the carpet and a pain to get to...I dunno if it will be worth to DYI or just go to a shop? Any suggestions?

whitels

What's the factory emission warranty, 7 years? Hmmm, I might have qualified...

whitels

Denso Universal 4-wire is the answer especially for after-cat (rear) sensor locations. Snip and splice will save you time as opposed to lifting up the carpets and looking for the connectors and putting everything back.

Turboo

My car have these symptoms but the check engine light did not glow!!

azrick

I'm looking at the front O2 sensors - they don't look hard to get at but I'm trying to see where the wire goes and plugs in. Any pointers would be appreciated. Trying to get everything figured out before I tear into things...

cjs18

Here are some cuts from fairly generic SC430 service material that may be useful. Perhaps someone may have more specific wiring information.

tenspeed

iTrader: (1)

O2 sensors get sluggish before they start throwing codes. The slow feedback will cause a slow but steady MPG decrease. Search the internet for instructions for checking your sensor using a meter and torch. If your sensors are over 60-80K miles, consider changing them out.

One thing that will quickly kill the sensors is silicone so don't use ordinary RTV on the air intake system. Use stuff made for automotive use if you have to use some.