Top 20 1991 Lexus LS 400 Questions & Answers

There are 1 or 2 large fuses in the main fuse block near the battery. 100 amp and 150 amp usually. Pop off the clear plastic tops and check those. Most times those will require separating the block to unscrew the bolts that hold them in.

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If the solenoid is clicking when you turn the key its very unlikely to be a relay fault, the relay controls the feed to the exciter wire which must be working for the solenoid to be clicking. If you haven't ruled out the battery completely do so by attaching jump leads, if that makes no difference you ideally need to check for a volt drop between engine and battery earth terminal and also main starter feed to battery positive, (the latter can be a problem with difficult to access starter motors tho.) if all wiring is ok its most likely the motor itself, if you can get to it give it a tap with something and see if it makes any difference. If it starts after a tap then its most likely the starter motor.

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Check and clean connections in your fuse boxes with an electrical cleaner.Change burnt fuses and ensure there is contact on your fuses. Check connections of your crank and airflow sensors as well. Clean the sensors first and if problem persist ,replace with new ones. Then take your car to a diagnostic technician to reset and check other technical problems with the diagnostic machine.

probably worth checking code to get better ideas for diag

I would try a crank sensor

Sounds like some kind of short or loose connection in the instrument cluster. A few years ago I had a van that would intermittently decide to not crank when the key was turned even though everything else worked. I went online to a forum for that brand and model vehicle and did some searching for a no crank condition and found others who had experienced the exact same thing and described what was going on and how to repair it. I followed those instructions and found exactly what they described, performed the repairs which was the resoldering of some cracked solder joints where the wiring harness connected to the instrument cluster, reinstalled the cluster and never had another moments trouble. That was on a 1998 so your 1991 could be experiencing a similar problem. But instead if just taking things apart and trying to find the problem, go to a Lexus forum and do a search for something like "temp guage maxes out when key turned on and starter stops working but then starts but reads 10 MPH too high after tapping on top of dash". You might have to try different wordings to find whay you want but I'll bet you dollars to doughnuts somebody else out there has had the same problem and talked about it on the forum. You can even just Google your question but you'll get answers for all kinds of vehicles and not even remotely similar problems. Good Luck.

More then likely your vehicle has a parasitic drain on the battery . A control module may not be powering down or something is on in the vehicle. Testing the electrical system like in this video is the way to find out . The BEST Way TO Perform Parasitic Draw Test

Be sure you check engine oil level often. The low oil sensor will disable the ignition. If you turn A/C on the cooling fan should run continuous, Check the fan relays. Make sure coolant level is correct at recovery bottle, never open radiator cap. A scald hazard exist, be careful. This car is old and complicated, and is beyond your skill level to repair. Try to inquire here for advice, whenever possible. Don't throw good money at bad money

Try changing the fuel filter? I would also try reading any codes that may have set. Parts stores like Autozone will do that for you for free.

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Possible air block or you may have by mistake installed thermostat up side down. Also make sure cooling fans are working

Sorry, your radio has died.. I can fix them, but I don't. Cheaper for you to get a new after market one. If you have an amp, bypass it or replace it also.

replace the coil as it may be over heating from internal short

check engine light is obviously telling you that you need to take to a lexus approved mechanic who will have the diagnostic equipment for your age of vehicle which is known as OBDI , there are many reasons for these symptoms mostly electronic so would need to actually be with vehicle to help better

Could be a bad brake light switch or the solenoid itself or wiring. See if brake lights work. If they don't then check brake light fuse, if thats ok then check at the brake switch for power or jump the two wire plug lights should light and shifter work unless solenoid bad. Good luck

Most all pressure regulators are located on the fuel rail under the hood. It should have a vacuum line attached to it

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