Replacing 02 Sensors '93 Ls 400

toothguy57 · August 19, 2014

I own a 93 LS 400 that I purchased new in 93 and it has 118,000 miles on it. I have taken reasonably good care of it, never missed an oil and filter change and have used a full synthetic oil for most of it's life.About 2 weeks ago the check engine light came on and I took it to a Lexus dealer in Santa Clara CA. The estimate for the replacement of 2 sensors (I am not sure whether they are upstream or downstream sensors) was $957.98. This was $524.58 for the sensors , 387.50 for labor and 45.90 tax. I would be most appreciative of some help/advice regarding the following:

1. Is this price reasonable?

2. I have checked Rock Auto for the sensors but at this point I do not have enough knowledge to select the correct sensor since there are several listed and they do not list the OEM part numbers. However, they range in price from peanuts to the most expensive one at $118.00. At $118.00 it would seem that the dealer is charging over twice the price. Any sugestions on how to select the correct sensor ?

3. Since I don't have a flat rate manual I don't know how much time is involved in replacing the two sensors. Any comment on the charge for labor will be helpful.

4. I am 82, retired but am in good physical condition and have done a lot of my own maintainence over the years. I have retained some tools, mainly a fairly extensive ratchet and socket set , torque wrench, box end and open end wrenches . I do have a volt/ohm meter also. I also have a set of ramps.

5. Finally, with the above information, am I crazy to even contemplate attempt doing this myself assuming that I can select the correct sensors?

sha4000 · August 19, 2014

First read this tutorial and bookmark the site for future repairs.

http://www.lexls.com/tutorials/EFI/mainoxygensensor.html

Second whether it's the upstream(before the catalytic converter) or downstream ( after the cat ) you should be looking at the Denso sensors on rock auto.

If your in reasonably good shape and have a jack, jack stands a ratchet and sockets I would recommend you do it yourself and save the money. I must warn you though that the downstream sensors require you to pull back the carpet in both driver/passenger foot wells to get to the connectors but if you read the tutorial you already know this, good luck.

toothguy57 · August 19, 2014

Thank you so much for the information. I have printed out the tutorial. I dislike being a pest but I have another request for information.

1. The tutorial dealt with replacing the right and left main sensors. I assume that main means the upstream sensors since they would be close to the steering rack. Am I correct? Also, the tutorial did not mention anything about replacing the downstream sensors and having to pull back the carpeting. Is there any special knowledge or technique involved in doing this ? Once the carpeting is pulled back are the connectors obvious ?

2. Should I be concerned about great difficulty in unthreading the old sensors/ i.e. fused ?

3. Since you suggested that I consider the Densco sensors I assume that all good quality universal sensors are compatible and will function properly. Is this correct? Rock Auto lists several when I requested sensors specifically for the 93 LS 400. They ranged in price from extremely cheap, which I would not consider. to the top price of $118.00.

Finally, I have not kept a record of the gas milage except that quite recently I have become aware that the milage is really terrible i.e. 13-15 mpg and for most of time that I have kept track of it ,t has been 17-18mpg city and 23 highway. Would these sensors be the culprits ? Again, I thank you so very much for your prompt response.

paulo57509 · August 20, 2014

I replied to to this topic yesterday but it disappeared after a few hours. :wacko:

O2 sensors typically come in two styles. Universal and OEM fits. The universals usually don't come with the connectors. They require you to remove the connector from the old sensor and splice it onto the new connector. The OEM fit sensors come with the connectors already attached. Hence the price difference.

Since Denso is the OEM for Toyota, I'd be inclined to use Denso replacements that have the connectors already attached.

http://www.rockauto.com/catalog/x,carcode,1187489,parttype,5132

Denso P/N 234-4211 upstream (OEM P/N's 89465-24050, 89465-50010)

Denso P/N 234-2011 downstream (OEM P/N 89465-50050)

Crawl under the car and take a look as part of your assessment for doing this yourself. According to the info at Sewell Lexus it appears that your car has four O2 senors. Two upstream (left and right) and two downstream (left and right).

I'm pretty sure the Denso part numbers above fit either the left or right side.

http://lexus.sewellparts.com/oem-catalog/8401MEM549-Electrical-LS400-1993.html

Did the estimate you received from Lexus Stevens Creek state which sensors needed to be replaced?

Edit: Regarding the dowstream sensors; it appears that the downstream sensors on my '98 look similar to the ones on your '93. I'll dig out my service manual and check on the replacement procedure. My guess is that the sensor connection under the carpet is going to be obvious.

sha4000 · August 20, 2014

Paul has found the correct sensors for your car and they are Factory OEM sensors and I believe he answered your question about why the prices vary btw aftermarket and OEM. If your willing to splice and re-wire the connector which is not terribly hard but you do have to do this underneath the car since there is no way to remove them, then re-wire and replace unless your going to tear up the boot that plugs the hole in the floorboard that they go through If it is the downstream sensors. It is obvious once you pull back the carpet since the plug for the sensor sits right on the of the radio. The upstream ones should be easier to fit the aftermarket ones since you should be able to unplug them and then remove them to do the work.

LSPaul · August 21, 2014

Odds are that the upstream O2 sensors are the ones that have gone bad. The LexLs tutorial's helpful, and once the car's up safely on stands or ramps, it shouldn't be too tough a task. I've had to replace both RH and LH sensors (okay, I've had to replace the LH sensor twice); it took well under 30 minutes for the whole project, per side.

Best,

Paul

'93 LS, 276k miles

sha4000 · August 25, 2014

Here's the pics you requested.

The first is the location of the drivers side downstream sensor. The second is the passenger and the third is a pic with the scuff plate rim removed. I used white so it would be clear against the black background. You can clearly see the holes that the clips pop into.

toothguy57 · August 25, 2014

Many thanks again. I am about ready to order the sensors from Rock Auto, liquid nail 2x4 blocks to the garage floor so that the ramps don't slide when I drive the car onto them and possibly purchase a 22 mm wrench for the sensors since it looks like the access is too limited for any thing else ie socket and rachet. Wish me smarts and some luck. Thank you again

landar · August 25, 2014

Hmmm, I thought I had replied to this thread but the posting is now gone.

Charles, you may be able to borrow an oxygen sensor wrench from your local auto store. They are made with a cutout to get around the wiring. Can't hurt to stop in and ask about it.

I agree about going with the Denso sensors with correct connectors so that you do not have to mess with cutting and stitching wires. I am not wild about Liquid Nailing 2x4's to the garage floor but if it makes it safer....ok. ;-)