My 98 LS400 had an issue of randomly turning off and all the lights when there was more current required, that is, all the lights in dash, stereo and screen would turn on and turn off at high speeds, say when I use a turn signal. Or sometimes when I press brake lights (while driving in slow speeds or when it rained), then the whole car would turn off and on -- I can feel the engine losing power and coming back alive after a moment. This has been happening for the last four or so months. Today I suddenly lost all the power when I taking a left and my power steering got lost power too. It was showcasing the same symptoms as above before this happened - that's is all lights went off and all error messages appeared in dash and car would lose power and came back alive, the tacho dropping to 0 and coming back to 1000+ rpm.
I was able to cruise and pull over, now the car will start and comes life for breif few seconds and battery lights turns on and dies. I did this four times, same thing - starts, alive for few minutes, if I try to put it in gear or leave like that for few seconds, the car dies and battery light turns on dash. The car has 257k miles and PS Pump has no leaks as it was replaced in 2019. I'm not sure if this is a bad ground or something else. Any idea where to start?

 

I worry that the battery post and the terminals as well as thick cables end are not electrically connected well due to the Galvanic corrosion. Aged cars often have this problem.
I'd inspect all of those and polish the surface of metals especially the thick cable's end from the fuse box first.

 

How can I rule out it's not alternator?

I need to get the car towed and probably inspect the post. Thanks for the tip yamae.

 

Timestamp:


But yes. Start with the terminals first. They could be corroded, or even simply loose and just need to be tightened. Cheapest and easiest solution it requires $0 and doesn't require you to tow the car.

If that doesn't work, then the rest of the video is the standard troubleshooting guide.

 

Also does the ecu throw any code when MAF or throttle body is unclean?

Since my transmission was hesitant shift (knock sensor code), I used to rev it above 3k rpm for 15 secs to make it shift. So I am also wondering does this mean a rich air fuel mixture and clogging throttle body? The transmission also has p500 code apart from knock sensor code.

 

Obviously, there's a major electrical issue. The first step is to inspect the source of electrical power which would be the battery and the cables attached to the battery which supply electrical power to the entire car. Once the battery is eliminated as a suspect, you can then move on.

I think all the other issues are symptoms of something upstream (the battery/charging system).

Ruling out the alternator (or any other electrical issues) requires that the battery be in sound working condition. Otherwise, any test results performed with a marginal battery is meaningless.

 

You're asking about the MAF is step 17, we're on step 2. Inspect the battery posts.

Don't MAF's usually throw engine codes when they die anyway?

 

Welp. You all are right. I had some slight white fuss on my negative terminal. I cleaned it with wire brush and disconnected MAF just in case. It started right away. Can't believe I ignored such a simple thing forever assuming it was a complex electrical issue. Lesson learnt. Maybe I'm gonna venture into this forum often.

the code was 325 for MAF and went away when I reattached the connector.

Thanks all. I will re open separate thread for transmission not shifting but I gotta rewire my spliced knock sensor hack.

 

Glad you got it solved! There's a wealth of knowledge here, it's been an invaluable tool to learn from people here over the years for myself personally.

Yeah you want the car to have a stable electrical system before you start trying to diagnose other components. Weird stuff happens if the source power is weird.

But yeah start with the simplest and cheapest item. You don't replace the engine if the car doesn't start right out of the gate without any testing. You make sure the battery is charged. Is there gas in it? Is the starter motor working. Even if it's so stupid and unlikely to be the issue, spending $0 or nearly $0 is a lot better than a silly expensive job that didn't need to be done.

 

Thank you for steering me in right direction. I was thinking the alternator is time bomb. I got it tested at AutoZone and they said the battery and alternator is good.

 

Yamae is the one who first originally said the terminals, I just agreed on him and offered a followup to that. He's the man.

 

I mean thank you all.