okay so ive got a 2000 lexus GS300, and had a major issue with my VSC light saying "VSC ON and VSC OFF" simultaneously. The codes it read me were for the TPS sensor, which I replaced, and did not solve the problem. I have a spare GS300 Platinum addition a friend of mine totalled from the rear end, and gave it to me for free. So I replaced the TPS and that solved the issue for about a week. Shortly after, the lights sure enough came back on, and again my lexus would show the symtoms. The car would get into second gear, and only into second. I said forget it, im replacing the entire throttle body. Issue SOLVED!.......WRONG!!! again about two week later, everything came back. I have a system in my car that drains a lot of energy, (my fault for no cap.) and soon after, my alternator began to act up. ( Whining noises upon start up, that never went away) Well as we know, once you replace the TPS sensor, you have to adjust the voltage correct? well i replaced the alternator, and ladies and gentlemen! it turned out my TPS senssor was not getting the correct voltage sue to my sterio, as my alternator was also going out. I've heard many people having the same issue and taking there cars to the dealer, then once getting there car back, all lights shorty came back. So what solved my issue? AS I KNEW AND CALLED! Voltage issues.... all I needed was a new alternator, obviously because mine shortly siezed after...and there you are... it WAS NOT my TPS sensor, and was NOT my throttle body... all it came down to, was...VOLTAGE ISSUES! I cant recall the codes it broughgt up, but i will post them as soon as I get home. Feel free to ask any questions as I am very experienced with these cars due to mine giving me every problem in the book. hope this helps ya'll!

 

Good advice, thanks.

 

Glad you got it fixed.

Keep in mind caps are band-aids and though it can help the amplifier get the surge power it needs it's still just another device adding load to your stock battery and alternator. If you are really dropping that much voltage from a large stereo the best thing you can do is add a second battery and charging isolator just for the stereo. The isolator will still allow the alternator to charge the second battery but completely keeps the amps and second battery from interfering with the rest of the cars electrical system. And if you play the stereo with the engine off til the second battery dies the car battery will still be charged and you won't be stuck.

 

Thanks for posting.
I wish Lexus used a better way to give us a low voltage indication.
I use a onboard voltmeter to monitor alternator output via Scangauge.
I have noticed that when my alternator was going out, no output at idle, there were no dash lights given, even though my voltmeter read under 12 volts with the motor on.

 

Thanks for the replys guys! so the code it brought up was p1120 which was the TPS code, which indeed was incorrect, in a sense, because it was not the TPS sensor that needed replacement, it just was not recieving the correct voltage due to my alternator going bad. It really is a hastle when codes are brought up, but leave you with a handful of actual problems it can directly be, leaving you in the situation I was in, trial and error. Like you said Frank, i wish lexus used a better methode of indication for lose of voltage, rather than bringing up a code for whats being effected by the lose of voltage. I as well used an voltmeter and tested my car with no stereo on, then stereo on with the subs turned up. The results were unreal... voltage was low to begin with even know I have an amazing battery, but right as I turned the stereo up, voltage went down to just about 10 volts if i can remember correctly, if not lower. Shortly after, my alternator siezed on me. My car was surging at red lights, and when i turned my A/C on as well.... this caused a mess of problems as you guys can see... where to start right? If you run into all sorts of lights tripping on, first things first with these cars lol... CHECK VOLTAGE! It will send your cars going crazzy, as well as you.

 

Thanks for the Advice! sounds like a definite solution! but as far as running another battery, I dont really see a capacitor as a band-aid..If you have an adequate battery suited for the stereo system application you may have, and an alternator thats up to par, a capacitor will definitly solve your voltage issues when it comes to having that voltage there on demand for whatever your amp may draw. If you have a high powered system or your amplifier doesn't get enough power to it on demand, which is easily shown by the dimming of head lights or incar lighting, a capacitor's main perpous is to charge and store that energy thats being demanded by your amp, with out taking the extra voltage from your battery which in turn will deprive your cars system from the correct voltage needed to run correctly. Making sure you have a capacitor installed will prevent any damages to your amp and other audio components, as well as your cars main CPU components as well... Caps work amazing when it comes to avoiding this situation.. more of a suturing technique rather than a band-aid.

 

@statix04--so your cause was a weak alternator?

Here's my situation.
98 GS4 184k. No suspension work in last 12 months. Stock suspension. No leaking fluids

2 months ago car wouldn't start one morning. Jumped it and took it to have the battery tested. Tested good but needing charge. Charged battery and all was good.
3 weeks ago same issue. Cleaned terminals, added distilled water to battery and put on charger. Wouldn't take a full charge so installed a new battery.
Yesterday morning started the car and got a loud humming noise from engine. Humming speeds up with RPM but gets quieter after motor runs a while. (Traced the humming to the area around the P/S pump and/or alternator.)
Yesterday afternoon on my way home the VSC, ABS and VSC OFF lights come on. Car seemed to run fine. Got home, shut off car and re-started. No VSC, ABS or VSC OFF lights come on. All is fine except for the humming noise is back this morning.

I guess the next step would e to have the alternator tested.
Any other ideas?

TIA,
JimA

 

Buy a multimeter, (voltmeter) and learn how to use it.


A multimeter is used to measure voltage (ac or dc), resistance (in ohms), and other features depending on capabilities.
The basic digital multimeter will perform many functions as well as the best tools in your tool box for electrical testing anywhere.

 

I have a voltmeter. What would I test for? Lack of voltage when running?

 

Took the VM to the battery. 12.56volts engine off and 14.00volts running.

 

Not quite. If the alternator is not keeping up with the demand from the audio system, adding an isolator and additional battery will not solve this problem - the alternator still won't keep up. And since the isolator will switch between both batteries to charge them as the controller tells it to. It is true that having an isolator would allow you to keep the system from leeching from the main battery, but if the alternator is constantly charging the aux battery, it may end up depleting the main battery due to lack of charging while driving. Now, if the alternator is keeping up under most usage but not when really pushing it hard, an isolator and battery may help, but it doesn't sound like this is the case for him.

Uh, no. If the alternator is not keeping up with the battery, the cap won't be getting anything and is another load. Keep in mind that a cap provides current at a specific voltage. Since most caps are typically at a higher potential (V) than batteries, they are the last in line when the charging system is operating, but also the first thing depleted when an amp hits. Once depleted, it needs to recharge. If the battery is also asking for a charge by being at a lower potential, the cap is simply sitting there. This is why they are considered bandaids for systems where the alternator is not keeping up with normal operation. If the alt is keeping up with normal operation but not the heaviest bass hits, a cap can help. Clearly that wasn't the case for you, but it sounds like it was just a bit off, not too bad.

BTW - good for you for sticking with it to find the problem. Troubleshooting can be a PITB, but it takes discipline.

Big Mack

 

This is most likely an alternator issue. i was having the same issue then replaced my alternator and now humming is gone... unfortunately i also had some suspension work done when i replaced my alternator and i think i damaged one of my sensors so my vsc/abs lights are still on... but if i were to guess i would say alternator..... after replacing your car would respond better too... because im sure you also got a drop in power

 

Check the speed sensors

 

Who are you responding to?

 

Good find. Im having exact same problem and alternator is putting out 10.2v max....