Diagnostic Codes

[muragrove]

Does anyone know how I can retrieve and read the engine diagnostic codes on my 1992 LS400? The check engine light recently came on but the car runs fine. I've already checked the gas cap.

[Larry M]

Hi

You can find the codes and some instructions at www.batauto.com. Look for the pull down menu "Technical Trouble Codes".

The hardest part of this is finding the terminals to jump. It can be done by a novice.

Good Luck. I hope it is nothing serious.

Larry

[muragrove]

Thanks for pointing me to that site. I didn't know about it. The dealer already scanned it and cleaned my very dirty EGR valve for $160. Had I known how easy that was I might have done it myeslf. However when I got the car back the check engine light was STILL on. He told me that my O2 sensor needed replacing for $320 or it would not pass my state emission check. As it happens, I was on the way to get an emission check anyway so I rolled the dice, left the O2 sensor alone and it passed with flying colors despite what the dealer said. Now I would like to read those codes myself and confirm his diagnosis, and now that I have have some time, perhaps replace the sensor myself.

How can I find out how many O2 sensors my 92 LS400 has and where they are located? Are they simple to replace? Any adjusting necessary once they are replaced?

I had an O2 sensor go bad on a 93 Sedan Deville and the gas mileage immediately went to about half it's normal range. That isn't happening on this car.

[Larry M]

Hi

Sorry I didn't respond to your post sooner. I have a 2002 GS 300 and don't normally read this section.

My guess is your O2 sensors are OK or you would not have passed inspection, but who knows, these cars are so complex.

One thing to check. Make sure the check engine light was reset. If they are not reset they will stay on even if the problem was fixed.

If you want to do your own work, you need a service manual. They are very expensive through the dealer (hundreds of dollars). I got my CD manual on ebay. Not as easy to use as a paper manual but OK. My manual is in two volumes. I don't know about yours. I got Volume one for $30. Just go to ebay and search for you model manual. you probably don't need you exact year. For instance, all the GS 300s are about the same from 1998 to 2002.

By the way, my model seems to have four O2 sensors.

Good luck and try not to let the dealers screw you.

Larry

[muragrove]

Thanks Larry,

Good tip about a CD based manual on Ebay. I never would have thought of that. He said he reset the sensor but I'll try doing it again. I just found (from a tip on the previous post) how to read my trouble codes and will try that this weekend when I have some time. I'll try to reset the light at that time as well.

Bill

[kulat]

Muragrove, I going thru that problem right now. I have the books, I have done reading the code I have done some of the procedures and still hit the wall. This Car is heavilly riddled with sensors. I just could not spend a lot of time working on it and decided to sched a dealer appointment. After seeing the prices on this thread. I will try again. How to read the code is to short TE1 and E1 on the terminal diagnostic port on driver side-left bottom or under hood top of engine, plastic cap labeled diagnostic towards the left front. flip the cap and short terminals with a piece of wire. Turn on ignition key and count how many times light blinks. Mine read two blinks a pause then 5 blinks. Code led me to book on Section TR8 - code then takes you to another page TR?? forget. Reset Check engine light by removing fuse under hood about left in front of coolant reservoir. remove plastic cover and remove fuse EFI about 2-10 sec. plug back in and pray light doesnt come back on. My prob. led me to check speed sensors on left bank and right bank known also as No. 1 cyl sensor and No.2 cyl sensor respectively or wiggle all connectors to sensor. Lots of plastic covers and bolts. Finally, I gave up the guess work. Next is also the fuel mixture sensor or O2. Hoping my dealer would fix this in no time. Your post scares me. Later

[muragrove]

Hi. Thanks for the info. What 'books' are you referring to? I've been too busy to try this yet. Maybe tomorrow. No reason to be scared, it's just a car!

Bill

[kulat]

this the factory issue Service Manual LS400 book vol. I . Its the damage to my pocket I'm scare about thats why I'm here on this forum. You know there's sharks out there. Ill give you details and pages tomorro

[kulat]

Muragrove. I had finally decided to bring my LS400 to the dealer. The service manual book was good and my findings was right all along. My oxygen sensors were bad as indicated by a code 25 for lean fuel ratio mixture. code 26 is for rich fuel mix. cost me about $75 for each sensors. I had two replaced. They are located right before your catalitic converters. You can do it in 15 mins. Just for the sensors for them to do it will cost around $375 for the labor. If you're still wondering how to read the code. Well, get a piece of wire and short pins Te1 & E1 in your TDCL port, turn the key on and start counting the blinks on the check engine lamp. as explained in the batauto.com. OR you could just bring it in for $85 diagnostic. they will tell you whats wrong and just fix it yourself.

[muragrove]

I finally checked my code and it is a 25 (lean air-fuel ratio). Based on what I read here and what the dealer told me, that means a bad O2 sensor. I went to buy one from a NAPA parts store and they told me I have two, one before and one after the catalytic converter. He also said they are simple to replace but it wanted $140 for one of them and $110 for the other so I'll look for another source for those. How do I find and access these? They sound simple to replace if you can find them!

Bill

[muragrove]

The dealer told me there are TWO Oxygen sensors in front of and another two behind the catalytic converter. How do I determine which one is bad or do they always get replaced in pairs? And how to tell which one causes error code 25?

Bill

[kulat]

both oxygen sensors will eventually wear out from heat. Since the book does not specify which side sensor is worn out. I assume both send the same signal to the computer in the same circuit. You can try one first and reset the code. but to save you the trouble of lifting your car twice why not replace them both. Its underneath the car and they look like spark plugs. change them both so you wont be bothered by it for a long time.

[muragrove]

Dear LS400 Fan,

Thanks for your note. Have you seen or replaced these sensors yourself to be able to give me a better location? Just knowing it is UNDER the car helps!

As for why not replace both, since this is a DIY project, it's simply cost. I'm out of work right now and if I can save the cost of an expensive sensor, I need to do it.

Bill

[kulat]

yes it is located right before the catalytic converter if you know how that looks like. from the exaust manifold. about the dashboard area. the other end of it has a snap on plug for the electrical.

[muragrove]

Thanks. This weekend - under the car - replace the sensor!

Bill

[muragrove]

I finally replaced my front oxygen sensor. There are two of them. One looked pretty new, the other looked old so I assumed that one had already been replaced by a previous owner and replaced the older looking one. Then reset the error codes and it worked!! I've only burned a 1/2 tank of gas since then but it looks like this may have increased my gas mileage about 20% as well so that's a bonus. Thanks for your help everyone.

Bill

[wolver1ne516]

Manuals are also available At sewelllexus.com and (cdrom)AllJapaneseCars.com :D

[Jungle]

Muragrove,

Had my '92 LS400 fixed today at my dealership. Had a check eng light with intermit. engine cutoff at low RPM. Diagnostics showed code 25. (My dealership does free diagnostics). They replaced the front O2 sensor on the right side (Our cars have 4 total - 1 fore and 1 aft each of the two CATs. Total cost 240 - 190part / 50 labor. Car is back to her old happy self.

Good Luck.

[Jungle]

Sorry Muragrove. Didn't see page 2 before I posted. I'm a rookie to LOC. Glad to hear your girl is up and running!

[Jungle]

Now I just saw the dates on the other posts.

OK, so I'm talking to myself, but at least I'm learning.

I'm a Marine. I need more pictures.

[SKperformance]

not really

i am here,lol

There is good and bad advie in this thread so beware before attempting any of the above.

the 2 digit codes are from obd 1 systems and they need someone with techincal expericane to repair them as you NEED to measure values with a meter.

Also a running lean is highly unlikely from an o2 sensor more of an egr problem

the o2 sensor each have there own wiring to the computer or else it would be a waste to have them . It just measures the temp for burn exhaust gases. The one before the cat measures the engine burn the one after verifies the cat is working.

hot mean lean rich means cold but you need to find out why.Unlike an obd2 system which identifies specific sensors this one does not ,It needs proper knowlegde to decode it.