Jeremy M.

It's the only thing that jumps out to me. I won't give a concrete yes/no because frankly, I can't be sure without going and performing the tests outlined in the manual on your car.

I was sifting through my service manual searching for my ECM location and came across a section on the wireless door lock system that I hadn't seen earlier; keep in mind that the component locations aren't guaranteed to be the same; for example, a quick (possibly unreliable) search says that your model year will have the wireless door lock ECU in the rear passenger door lining instead of behind the glovebox. The only possibility I can think for a connection between the problems you have is the body ECU, so I've included attachments of the service manual sections for my model year, and hopefully the components are similar enough to push you in the right direction. The below picture is what I found for the location of your generation's wireless door lock ECU be-152.pdf be-160.pdf be-169.pdf be-171.pdf

I can't promise a fix for a slow downshift because I'm not 100% if it applies to the LS400, but some systems use inputs from both the TPS and MAF, so cleaning out your filter and spraying down your MAF (with the proper cleaner) might help a bit. Even in my 98, there was some delay, so I doubt it would be gone completely with that, but it should only take a second or two instead of four.

Thank you very much- that troubleshooting chart in particular is just what I was looking for. My own service manual didn't seem to have the files for that section. I do have an OBD-II scanner with live data, so I'll go on through the process and check over everything.

I don't see the gas affecting it all that much if I'm honest- the engine does run, and revs fine. It just doesn't drive; the engine will rev all the way through the tach with no weird hesitations, but it refuses to give power to the wheels. That being said, I'm definitely willing to try siphoning out the tank and filling it with some fresh stuff, since it can hardly hurt it. If you're willing, would you mind explaining how rotten gas would affect the engine, just so I can try and match it up with my symptoms?

If anyone is able to add their two cents, it'd be appreciated- my latest theory is that the torque converter is starved for fluid, but I'm unfamiliar with the pumping system for the transmission fluid, so I don't know whether the torque converter will be filled with an idling engine. In my service manual, it shows the torque converter refilling by taking it out of the vehicle, but that's unfortunately not a possibility for me right now. Does anyone have knowledge on whether a torque converter left sitting for 3-4 months without running would A. Drain it's fluid back into the transmission pan (there was no fluid leaks outside of the transmission) or B. Bleed out air in the system without me needing to remove the transmission and fill it manually?

The LS400s aren't terribly difficult to work on, under the plastic beauty covers there's at least some working room. Honestly, one of the most frustrating things I've run into on them are connectors at the top of the engine being exposed to heat for 25 years and cracking instead of removing in one piece. One of the bigger headaches for 1UZ engines would be replacing a starter, because that's nestled right in the valley of the engine, and you'll need to remove the intake manifold to get to it. Otherwise, most repairs are fairly straightforward. I'd advise against aiming a parts cannon at one though, since some parts can get pricey. Additionally, I'd be wary of the condition of a non-running car, insofar that I'd want to go check the codes myself at minimum. I also want to point that in the picture of the engine compartment there's a couple points for concern other than whatever ignition problems it has, where you can see the coolant reservoir is looking low/empty, and the brake fluid looks very dark. A car won't last 270k without a decent bit of care put into maintenance, but if they've gone lax in the last 50k, you'll be playing catch-up for maintenance before components start failing.

I actually had gone and replaced my reservoir hoses recently during a head gasket job as they had gone hard. It was on a '98 as well, and I found that some parts stores have bulk hose that fits well. The thicker hose fit nicely with a 5/8 in diameter bulk hose, and the thinner one fit with a 3/8 in hose. I'm not sure what trouble Paulo ran into with the 3/8, but it was a snug fit with no lube necessary for me; just a little wiggling and pushing. Both are short enough with no large bends that imo molded hoses are really not necessary. Just make sure to check that they are made of a suitable material, not something that will absorb the ATF or be degraded by it.

I have the generation right after yours, (1998 model), but a quick check of the service manual from my generation yielded a couple possible fixes- attached is the troubleshooting chart in a screenshot, and the relevant pages in case they help for your year LS. There is a transmitter inside your fob that might have gone bad, which you can get a replacement from Lexus, and it looks like there's a description of how to program your new fob to your car, which is also one of the files. Best of luck figuring it out, unfortunately, I think this is about all I can do to help through the internet. be-153.pdf be-164.pdf

Edited to remove what little I said, I wasn't really thinking, and Bykfixer is really right lol.

The relay really should be shut off, disconnecting power when it's not being activated. I'd check that the relay is functioning as expected by jumping power to the switch side and testing for continuity on the load side, and making sure it shuts off with no power to the switch side. You should also hear an audible "click". If the relay looks to be working fine, I'd look for a wiring diagram next, and find anyplace where power could be shorting to the relay to keep it in the "on" position.

That sounds unfortunate, but if you have some basic tools and there's a junkyard or pull-a-part nearby you, swapping out with a used PS pump isn't too difficult. Not certain about earlier models like yours, but my '98 had one 14mm nut on the front and two 14mm bolts accessible from the bottom, and then just disconnecting the hard lines. A used PS pump that you don't see hugely built up with grime (you're bound to see at least some grime on a nearly 30 yo car) is probably still working, and if you're feeling adventurous, you could try to rebuild yours.

If the ECU checks out ok, since you suspect the O2 sensors, you can try checking them with a scan tool that has a live data output- they're expensive, but well worth it imo. If you don't want to shill out $100+, you might find a friendly mechanic that will read out your live data with his tool, and you can look for one or more O2 sensors reading abnormally from there.

I'd eliminate the coils being the problem by switching them over to other cylinders and seeing if the misfires move as well. Check that the spark plug's gap is set correctly (1.1 mm), check for compression (spec is 142 minimum PSI 178 nominal PSI- you can rent a compression tester free at most auto parts stores), and check that there is no source of a vacuum leak, especially towards the back of the intake, since that's where both 7 and 8 are located. I'd also check the spark with an in-line spark tester to see how strong the spark is. A strong spark should be blue-ish in color and easily visible in daylight.

You might try blowing compressed air through the line, in from the hose leading out the fuel pump (assuming the fuel pump is working) and letting any gunk clear from the other end. Another thing to check, although I'm not 100% on this, is whether the key is programmed to the car properly. I know that the key, even if it will turn in the lock and crank the car, won't ever start it without being programmed properly as a security freature, but I'm not sure if it disables the fuel system or the spark without the programming.

I just finished resurfacing my heads after they warped, basically a full head gasket job per the service manual I have, and after starting the engine, everything sounded and looked good until I put it in gear to go for a test drive. Once in gear, it didn't want to move and had very little power. I couldn't climb the slight incline back to my driveway, and had to get a family member to help tow the car back up. I don't suspect that the head job was relevant, since none of the transmission connectors were even touched during the process, but I mention it in case it sparks some ideas. Check engine light presents with the single code of "P0500- vehicle speed sensor malfunction". I pulled both speed sensors (located on driver's side of transmission, part no. 89411C) and tested them both to see what kind of output I could get from them. I'm looking for either a better test of the sensors, or a way to test the wiring (continuity test or resistance, etc.). What I did to test the sensors was position them at about 20 thou from the chuck from my drill and spun the drill at it's top speed (an assumed 1800 rpm from specs, but I just thought I could get away with any speed as long as the process was repeatable). It isn't a completely accurate way of testing it, but since the three chuck prongs protrude from the center, as it spun I was able to get a consistent reading from both sensors of about 0.25 V AC. I unfortunately can't afford to parts monkey the diagnosis and throw two new $60 parts at the car without knowing it'll solve the problem, especially after spending near a third of the car's value on a head job, so if anyone has any knowledge of how to test or diagnose this, I would greatly appreciate it.