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Having an issue with voltage to the battery on a 02' ls 430. I have a computer reader that shows when the car is running down the road, that I get 13.8v at 1309RPM, 11.4v at 1604RPM basically the voltage at the battery is changing from above 12v to below. Could this be the battery, voltage regulator or the alternator? Probably any of the three right?
I had an autoshop (Mr. Tire) diagnose the issue and they found nothing (I think I wasted my money!).Before you ask me why Mr. Tire of all places, it was the place I made it too after sitting on the side of the road for a while thinking I would be stuck getting it towed...
The original problem: I was driving down the road and the car stopped running, completely. No codes, No warning nothing! Pulled over without power brakes or steering assistance, tried to start and there was just ticking... waited few seconds then noting at all, waited a min and the car started like nothing was wrong at all. Very odd.
Trying to fix the issue for good. Any ideas? So far I'm thinking of replacing the alternator then battery if the problem persists. Anyone ever heard of this issue?
If it dies like that, then I agree you should replace the alternator at the very least. The alternator output should increase voltage slightly as the RPM goes up, not trend down. If it trended down, then there is no alternator supply and car is pulling all its needs by draining the hapless battery.
Might also be a simple thing like bad alternator connection or ground, but I'm going to be alternator.
The battery is probably shot as well, if it was drained down flat supplying the system without an alternator's help.
Having an issue with voltage to the battery on a 02' ls 430. I have a computer reader that shows when the car is running down the road, that I get 13.8v at 1309RPM, 11.4v at 1604RPM basically the voltage at the battery is changing from above 12v to below. Could this be the battery, voltage regulator or the alternator? Probably any of the three right?
I had an autoshop (Mr. Tire) diagnose the issue and they found nothing (I think I wasted my money!).Before you ask me why Mr. Tire of all places, it was the place I made it too after sitting on the side of the road for a while thinking I would be stuck getting it towed...
The original problem: I was driving down the road and the car stopped running, completely. No codes, No warning nothing! Pulled over without power brakes or steering assistance, tried to start and there was just ticking... waited few seconds then noting at all, waited a min and the car started like nothing was wrong at all. Very odd.
Trying to fix the issue for good. Any ideas? So far I'm thinking of replacing the alternator then battery if the problem persists. Anyone ever heard of this issue?
Did Mr. Tire generate a diagnostic printout ?
Condition of your battery terminals and negative grounds?
They did not have any documented printout like I said I guess I wasted my money. Horrible to work with too on the price. I don't think they really worked on it for hours like they said. What really confused me was the car dies and when trying to restart the car ticks like the battery is shot. But then a minute later it starts without any issue at all. Sounds like a short somewhere but when its working the car works perfectly. I would also think a short would generate a code too but no codes at all.
I would swap out the battery for a new one first. Dying batteries do the strangest things, especially in cold weather.
It's also a heck of a lot easier to do than working on the alternator. :-)
Sometimes a load tester will tell you that the battery is fine, but if it has a cracked weld somewhere, then the cold can open up that crack and it will just die when it gets cold enough.
Sounds like the builtin regulator unit is partially dead. As you increase the engine rpm, the power consumption is increased due to the increased cycle of the injection and the ignition but the regulator controls the voltage and it should keep the voltage stable. A 02 LS430 doesn't have the charging control system and the generating voltage shows almost the same between 750rpm to 6000rpm. The voltage only varies some depending on the temperature. Your type of voltage down is mostly caused by the partially failed FET in the regulator unit.
You need better diagnostic tools if you want to diagnose this on your own and to not replace things that you don't need to replace.
With a basic multimeter, you can measure the resistance between your battery positive terminal to Terminal B of the alternator (the one with the thick rubber boot around it). This is a direct line, there should be no voltage drop and there should be no resistance either since it's a straight line. If you get intermittent readings, then suspect a broken cable and/or corrosion.
You can also measure standby/parasitic draw, extensively discussed on these forums and on YouTube. This will rule out something constantly draining your battery.
Once you eliminate the easy stuff, then you need to do a full charging/starting/battery system test. Assuming you don't have access to a Midtronics battery/charging system tester (many Lexus/Toyota dealerships use the GR8-series) or a friend/shop with a Fluke 500 series battery analyzer, you can go on Amazon and buy a much much cheaper Ancel BA201 or BA301 (301 does 6V in addition to 12V).
The Ancel units are reportedly not that accurate, but they'll give you a rough idea of what's going on. They can do a charge test and a crank test and show you the waveforms. You need the waveforms - testers that just show a number or a light leave too many possibilities out there. Now you can suspect or rule out the alternator and starter and diagnose further from there.
The Ancel testers show a digitally-calculated CCA available in the battery, which is less accurate than a real load test. It is just a quick check to compare against your battery's advertised CCA. If there is a huge difference and/or if the CCA is very low, then your battery is suspect.
To confirm that your battery needs replacement, you need an actual load tester like the OTC 3180. This lets you manually draw >100A via a toggle switch, which you should not leave on for more than 10-15 seconds. If the needle drops to the REPLACE zone by the end of the 10-15 seconds, then you can be very sure that the battery is bad. See
Sounds like the builtin regulator unit is partially dead. As you increase the engine rpm, the power consumption is increased due to the increased cycle of the injection and the ignition but the regulator controls the voltage and it should keep the voltage stable. A 02 LS430 doesn't have the charging control system and the generating voltage shows almost the same between 750rpm to 6000rpm. The voltage only varies some depending on the temperature. Your type of voltage down is mostly caused by the partially failed FET in the regulator unit.
Can you explain what is the FET? My Lexus just started doing this same thing. It drove fine this morning. But the when I got in it later, the battery was dead. While driving home it cut off a few times. It starts right back. What can this be? The battery is new. It has me confused
FET stands for field effect transistor and not sure if is in the regulator circuit or not. Make sure battery terminals are clean and secure. Carry it to advance auto or a place like that and they will check out your alternator for free. So you put a new battery in and while driving home it cut off?
02-18-21, 12:36 PM
Car died while driving down the road.
