MrGQ

Ok, so the check engine light on my SC3 just came on lately and I took the car to get a diagnostic. The mechanic that did it said that I have both the main and rear O2 sensors bad. My question is how many O2 sensors are there total and how should I go about replacing them? Are there two sensors in the front and two in the back? Should I replace all the O2 sensors at once or just the main ones? Also, is this something that I can do by my self and not take it to a shop? I'm just totally confuse and don't want to get rip off. The mechanic quoted me ~$450 for 1 new front and 1 rear O2 sensor (OEM parts) and installation.
Thanks in advance.

-MrGQ

awj

What year is that sc3? Your mechanic was telling you that your oxygen sensors are bad. Whether or not he is right is another question. Off the top of my head, I don't know about the layout on the SC3. I'll check my manual and post up tomorrow. It sounds right about the two sensors. I'll verify. If you don't know yourself - I'd recommend you get a second opinion and pay to have it done. You're sensors should put out a signal that can be chekced by multimeter, not sure if it is a voltage or resistance check. Go ask another tech is my advice for now.

SC300T

The book lists 2 main 02 sensors (one in each bank of 3 cylinders on the exhaust manifold) and one sub oxygen sensor in front of (or on) the Catalytic converter. The sub oxygen sensor is for US spec versions only.

This is from a 1992 SC300 manual.

I could have swore that I don't have the sub sensor (rear one) on mine, though--- because I replaced the midpipe and didn't find any 02 sensor there--and I assume mine is a US spec car. Perhaps some had it and some didn't. I think the OBDII cars (1995 -on) may have the sub oxygen sensor.

I'd replace the front two (main) sensors first and wouldn't worry about getting a Lexus brand one--- they all spit out roughly the same signal. Mine is actually a heated 02 that is made by GM--works fine. Autozone may carry a Bosh brand for this vehicle and save some $$$.

VQT

What year SC is it?
SC400 has 4, O2 sensors like SC300T described. 2 main and 2 sub, the sub rarely goes bad. You need to check the trouble code first and you can do this yourself. The following is from my 93 SC400 repair manual.
I paid $114 each OEM main O2 sensors because I din't know aftermarket has them. I would recommend bosh or any other after maket brand like SC300T said. A forum member replaced his with after market sensors after I did, I think it cost him ~$35-$45 each.

DIAG. TROUBLE CODE 25/26 FOR 93 SC400

There is a DLC1 under the hood. It’s a small black box with a cap covered located at the front left of the engine.
1. Warm up the engine to normal operating temperature
2. Connect terminal TE1 and E1 with a paper clip.
3. With a voltmeter, connect positive probe to terminal VF1, VF2 and negative probe to terminal E1 of the DLC1. Probe VF1 and E1 then VF2 and E1.
4. Warm up the oxygen sensor by running engine at 2,500 rpm for about 2 minutes.
5. Then, maintain engine at 2,500 rpm, count how many times needle of volt meter fluctuates between 0 and 5 V.
Results
Needle fluctuates 8 times OK
Continue at 0 V NG type I
Continue at 5V NG type II

Check Voltage between terminals OX1, OX2 and E1 of DLC1.

NG type I
1. Engine still at normal operating temperature.
2. Measure voltage between terminal OX1, OX2 and E1 of DLC1 when engine suddenly race to full throttle.
3. The voltage should be 0.5 V or higher at least once----OK
Need to perform this inspection within 1 sec.

NG type II

There are too much in formation to type in here. Need the whole repair manual.

There is another check for oxygen sensor

1. Start engine and warm up
2. After engine is warm up, let it idle for 3 min.
3. With A/C ON and trans. In D position (O/D ON) perform gradual acceleration within the range 1,300-1,700 rpm (centered around 1,500 rpm)
(Take care that the engine speed does not fall below 1,200 rpm when shifting. Gradually depress the accelerator pedal and kept it steady so that engine breaking does not occur.)
4. Maintain the vehicle speed at 40-50 mph (64-80 km/h)
5. keep the vehicle running for 1-2 min. after starting acceration.

HINT: If a malfunction exists, the malfunction indicator lamp will light up after approximately 60 sec. from start of acceleration.

NOTICE: If the conditions in this test are not strictly follow. Detection of malfunction will not be possible.

Good Luck and let us know the results.

MrGQ

Hey guys. Thanks a lot for all the info. Sorry for not including the year of my car. It's a 92. I think I'll go to Autozone and see what I can find there. I got a quote from the Lexus dealership and they were about $207 a piece for the main sensor. OUCH!!! I'm also planning on getting a new exhaust system so I'm going to ask the guy who is going to install it to also install the O2 sensor as well. I'm going to try to yank the code out myself to make sure it really is the O2. We'll see what happens.

-MrGQ

BriMcc

Try www.global4autoparts.com This a Canadian site and I paid $115 Canadian each. US$ would be alot less.