I have a sc400 Lexus. Have no idea where to buy repair manual or parts. Read below and please help.

dont get all done in by a minor glitch. fix the vacuum thing and any loose clamps and drive it if it's runnin ok.

I repaired all of the vacuum leaks. I do not see any more. I removed the neg of the battery for five minutes. started the car, drove around the block and a/c worked ok. Then all of a sudden, the car started missing, the a/c stopped, and it went dead. I got it back home, and I can remove the neg on the battery and re-install it, then the a/c works car runs great for about two minutes, then it dies. When I turn it back on, it is idleing much faster. And A/C does not work. Something is bad and the computer is finding it. I am not sure I can make it to the auto parts store in it to find the fault code

https://www.2carpros.com/articles/lexus-trouble-codes-obd1-1990-1995-code-retrieval-procedure

Try above link for trouble code retrieval.

ok, we started it from a cold start and it ran terrible, we pulled in a shop. The mechanic put it up on the rack and went right away checking dual catalytic convertors, resonators, etc.
Then they started saying that the check engine light would not respond or come on at all. They were wanting to keep the car at 80 per hour and go into the dash. (I am not paying for an idiot light, that would make me the idiot) They claimed at first the car was too old, that they had newer meters, then they tried and older meter and claimed the ECU wouldn't keep flashing long enough for them to get the code. Then he started checking the coils, one was newer and had been replaced, the other was original, so he ordered a coil. $215, out the door and the car ran great...until the next day. From a cold start, it takes three or four tries until it stays running, and when you go it has half power, running slow until it builds up speed. Then stopped at red lights it is idling higher, we pull over turn the thing off and go in a store or something and come back out, start it and it runs great again. After that, there are no more problems the rest of the day.

I am considering a plug job, and a fuel filter replacement and see if it helps. It can't hurt anything but my wallet, since I do not know when they were replace last.

Do you have coolant losses issues?
Check the engine compression and let me know the results. Do it on a cold engine.

ok, I had a compression testor, but since it is from the 70's, it has about had it anyway...no coolant lost...put in the plugs, All plugs looked the same, carbon with no damage, changed fuel filter, and found two loose vacuum hoses. They are like hoses that just got hot and they are plugged on, but loose. I pushed those way on really hard. Car was running great for two days, and then when the fuel light came on, added gas. Then it went back to it's old way of spitting and all that stuff. The A/C will not pull in the clutch when it runs rough and the RPM tops 1200 at idle and then it starts skipping and running rough from 1200 down to rpm of 600. The other day, it cleared up on its own riding down the highway and we had really cold air all the way home. I had another shop tell me it may be the a/c compressor dragging things down. But I do not have the a/c on all the time yet. I am still leaning towards these old vaccum hoses and will not stop until I am sure there is no loose ones anywhere. I would probably pay $700 for another a/c compressor and then it still do the same thing. So, ruling out the simple things are for me. I love being under the hood of this car. Everything is in such great order. I like organization.

Recheck the vacuum hoses. If there are loose, snip off the ends and reinstall.

I don't think you need a compressor. When engine idling speed is too low, the AC would not work. Since the problem affects the A/C, I woudl suggest checking the ECT.

well, I have been busy moving...the place where I lived was a gang hood, I had two tires cut and slashed, and a neighbor had water put in her gas tank. My car runs great most of the time, with the exception of startups. Sometimes it will start up and rev up and then it runs with no power at all. We have just gotten used to turning it off, waiting a few mintues and then start it again and then it is all right, while waiting we smell gas fumes.
And that A/c compressor quit. The clutch engages, squeals and then with a thump it stops and the light over the a/c switch starts blinking. I know the compressor is locked, I see the clutch slipping on in trying to move it. Otherwise Texaco gas seems to make the car run a lot better

Symptoms indicates a possible fault with the PCM or its wiring. It is intermittently not working correctly and restating sometimes solves the problem.

I got sick, and found out I have fainting episodes, or possibly seizures. So I have been away for a while.

The way all of this started, we have gotten used to turning the car off when it starts up and idles too fast, and the next time she runs perfect. It is intermittent...But now to the real worse problem. We will look for that first problem later, or may solve them both at the same time who knows?
We had the coldest air, until if got really hot...then one day there was a squeal under the hood. I noticed that the clutch is pulled into the compressor, but a large center piece with a bolt in it is not turning. It tries intermittently and this is what makes the noise. I put my gauges on it, and of course the compressor is not pumping. I took a large screw driver and the end of the clutch is like a magnet making the driver stick to it, however the cent part of the hub with the bolt in it will not turn, it appears to be broken off of the clutch, Could this be the case and I just need a clutch, or is it possibly a new compressor...makes me sick knowing it is so hot and I am so sick. I gotta have it cooling...The belt is ok and it all is turning, just not the end of this plate with the nut in it...I feel like that bolt and plate is what turns the compressor and makes it pump. Anybody?

Seems the clutch is bad and has detached internally causing the compressor not to turn. For some model designs, this can happen. With engine off, manually turn the center bolt with a spanner and if it turns easily, you need a clutch. If the bolt seems seized, you need a new conmpressor.

what I replaced was the clutch drive plate that went on the very front of the clutch and viola, A/C worked again

Good to know you have the problem fixed.

However, the speedometer stopped working while on a trip and the O/D light started flashing. Not many mechanics can test OBD I in Tallahassee, I found out that some one (Probably to sell the car) moved the check engine light so it would not burn, I went into the cluster and moved it from Trac Off to the proper place. Now the engine light stays on all the time, and even jumping out like the page says to doesn't make that light flash. I removed the fuse, I also removed the negative battery cable, and nothing changed to clear any codes, and to make matter worse, the very first problem I wrote you about has started again. You crank the car, it idles high, no power on take off, but that O/D light quit flashing. I tried to jump the terminals to check it, but only the ABS and Cruise lights flash off and on. The speedometer, odometer, and cruise all quit. Everyone says speedsensor. But not everyone agrees as to where it is, transmission, or tires, or more than one. I think I have multiple problems, and not just any mechanic can handle it, and we have NO LEXUS dealer in town. A Toyota Dealer that is it. I want to slap the man who sold the car, and my wife for buying it, it is the 2nd piece of crap she has bought. I will from now on pick the car MYSELF. I am sick of this one. And its age is the problem, no one has the crap to work on it, you have to order parts for it, and I do not have a credit/debit card, no repair manual, nothing. So what in the world could be causing all of these problems? I feel like running it into a dang tree

The speedometer not working is related to the O/D light flashing. When you bridged the diagnostic terminals, didn't the O/D light flash the codes?

When the MIL stays on, it could be a fault with the circuit or there are trouble codes. When bridging the diagnostic terminals, did it stay on or blinked.

You might have some wirring issues that needs some time and effort to resolve. I need to know the exact situation in order to be able to help you.

I would like you to list whatever things you need to do and we would go through them one by one. I am sure we can get it done since you know what you are doing.

Well, I do have a check engine light now, at least, but it burns all the time. I did pull the fuse, and neg on the battery to try and clear the codes. The light still stays on. Nothing ever blinked. With the car reved up again and no a/c that O/D light went off and stopped flashing. I bridged the terminals to try and get the codes from the check engine light, but it never blinked. I tried to bridge the terminals to check the O/D light and the ABS light blinked and the Cruise light Blinked, but it was just blinking, not codes. Yesterday, we drove it and a few miles into the drive, (before I fixed that check engine light) the car idled down, the a/c started working and then the O/d light went to flashing again. At no time did the speedometer ever work again, but the odometer has moved about 6 miles in the last two tanks of gas

Oh and I did notice that there was NO BULBS near that check engine light bulb...there should have been three, one for Trac Off, one for check engine and one for the AirBags...but there was only the one bulb. I would have to order the bulbs from Lexus, and there could be faults within the Airbag system, or any of the other bulbs that were gone. Screws were missing where someone entered that cluster and dropped the screws by not having a magnetic screwdriver.

The first thing you need to do is to check the wirings and confirm they are in working order. The MIL not blinking and others not flashing codes are most likely to be due to faults within the wiring circuit. This can also contribute to the faulty vehicle speed sensor. We need to get them resolved first.

The wiring diagrams won't show up well if I post them here and if you could let me have an email, I can send the PDF files to you.

As to check confirming if the MIL is working correctly, I can send the procedures to you as well. For all correspondence, please keep them here as we would like to have the history of what we have done to be here in one post.

I went to a transmission shop, the car started working good, and the a/c went to cooling again and the O/D light started blinking...the guy at the shop had the meter to check the codes but it would not work, but he did manage to somehow get the check engine light to flash...code 21, code 28, and code 71. He said it was O2 sensors, and EGR problems. Nothing showed up on the speed sensor, but I think you have to short two other terminals to make those lights blink. My email is [email protected]

http://www.lexls.com/tutorials/intro/codereading.html is what I am following to get codes, I stand corrected, the TE1 and E1 jumper should have gave that man a code for the speed sensor, and he said it did not, that is was probably the motor head in the cluster. That cluster did not come out, I tilted it to get to those bulbs because the steering wheel must have seized up gears, it doesn't want to move out enough. Something else I guess I have to fix, I see now this Lexus is something to collect, not something to rely on

The O/D light would only flash when the O/D switch is turned ON, meaning the light is not showing in dash when ignition is turned on.

Are you able to turn the light on or off when ignition switch is turned on?

Since you are able to get the codes to flash, the wiring schematics might not be necessary for now. You are using DLC2 for retrieving the codes. There is another DLC1 under hood which can be used as well. Refer to my March 19 reply for the link.

With or without the codes and the speedometer not working, we should start with some diagnostics on the # 1 speed sensor.


1. Test drive vehicle and check operation of speedometer. If speedometer is functioning correctly, go to step 3.

2. If speedometer is not functioning, inspect No. 1 speed sensor. Replace as needed. If speed sensor is okay, inspect circuits between speed sensor and combination meter. Also
check combination meter if necessary.

3. Access ECT ECU. Lift and support rear of vehicle. Turn
ignition on. Backprobing ECT ECU harness connector with DVOM, measure voltage between terminal SPD and ground. Turn rear wheel.

4. If voltage pulses between 0-14 volts, replace ECT ECU and retest. If voltage does not pulse within specification, inspect and repair
circuit between combination meter and ECT ECU.


Code 21 and 28 are common faults with both O2 sensors. I would send the files to you so you can check through.

I am supposed to be on crutches, so I am doing what work I can get to. This car started cranking up idled up high again, with the check engine light on and it won't idle down anymore, like it was doing in the beginning. Turning it off and back on doesn't work anymore. If you drive, you have no power, you use a crap load of gas, and maybe if lucky, it idles down, chugs awhile and then starts running perfect and the A/C starts cooling again, or you stop at the store and come back out and it starts up and runs perfect, just like before. I managed to clean out the EGR Valve, and blew out the filter and all on the EGR vacuum modulator. I removed EGR from the intake manifold, and the hole on the manifold was almost 75% clogged with carbon. I cleaned it out real good, except I am not sure how far up in there that hole goes. I can make the EGR diaphram move by applying vacuum on the hose. I removed the neg on the battery, and the fuse to the EFI for over 30 minutes, but the car started up the same way with the engine light staying on. I have tried to jump the terminals as per your March 19 post, and I can not get that CEL light to flash at all. I am about ready to think I should buy new O2 sensors as when it did flash, those were two of the codes 21 and 28. The email you sent, where are those terminals located? And where is the ECU, under the glove box or somewhere? It is so difficult for me, with a bad knee, and the muggy weather, I get sick trying to work on it, probably not thinking clearly and getting frustrated. But trying like hell to keep it together. I put a zip tie behind the steering column tilt gear so the steering wheel would go up and down, so I could get the instrument cluster out. I had so many bulbs out, at night I couldn't see the gas gauge. Temporary solution I rearranged some bulbs to light up most of the cluster until later, still no speedometer yet, I want to get the thing running right first. But I am thinking, what if all these problems are all related and are in the wiring and ECU like we have discussed? Then I will have my work cut out for me and it is going to be tough and bulbs will be the least of my worries

So, I think we should go back to the August 30th reply from you. Send me the wiring diagrams, and procedures to check the MIL and let me see if I can find out why the paper clip won't flash any codes. When the car runs right the O/D light flashes all the time even with the button pushed in on the shift knob. But when the car runs slugglish, that light goes out completely. I have tried several times to make those codes flash but the light just stays on and nothing ever flashes

Diagram shows location of ECU. The lights not flashing are usually an indication of a faulty control unit or bad ground circuit connections.

No speedometer reading could be a faulty meter cluster and that could cause the O/D light to flash and erratic transmission operations.

Just went on about a 30 mile trip, and almost home, the car cleared up and went to running ok. I ran in the house and grabbed the paper clip, and viola...code 21, code 28, code 71 on the Check engine light...and the O/D flashed a code 42. So Looks I am going to need those maybe those O2 sensors, something is STILL wrong in the EGR Circuit, and this time it pull up a Speed Sensor Circuit issue. I am getting excited cause I have never gotten any of this before.

At least we are getting somewhere.

Code 42 - # 1 Speed Sensor. Refer to Aug 29 post for diagnostic procedures.

You would need to perform diagnostics on the EGR system to find out what is wrong.