Question about 2000 Lexus RX 300

2 Answers

Car not getting electrical connection

I have a Lexus rx300 that appeared to have a low/dead battery. I jump started the car normally and while driving home noticed that all the lights (dome, headlights, panels, etc) were flickering while the engine was running. Also the gears were shifting roughly, when getting home I turned off the engine and tried to restart but no power (starter, lights, horn) were all dead. I replaced the battery with a new one but noticed that I was not drawing a spark when putting the negative terminal on, and again no power to anything in the car. Tried jump starting again and the car started right up but again all lights were flickering. tired reinstalling the new battery with no sucess like before.

If I have a bad connection (loose wire, blown fuse, etc) why would the car start when jumped? If the battery is new, why would I not have any power connectivity for horn, interior lights. A quick stop at the Lexus dealer suggests a alternator problem but that still does not answer why no spark on the new battery.

Not a dummy around engines but all these new engines rely on elecrtonics as much as mechanical equipment. All ideas welcome, thanks

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  • 3 more comments 
  • Mike Gray May 08, 2009

    First answer was very vauge with little to address the specific issue of non-conductivity with a new battery but connectivity with a hard jump start

  • Mike Gray May 09, 2009

    Hello: Thanks for the reply, I was able to jump start the car using the positive battery post and grounded to the engine block (bypassing the negative terminal) . Again the car stared right up and continued to have flickering running & interior lights, panel lights, etc. I did not drive the car to see if the rough transmission shifts was still present. upon shutting down the engine I put on the negative terminal connection and again nothing, no power at all. So I am convinced that it is not a cable issue but probably the alternator, going to have that tested tomorrow morning as I do not have a voltage tester. Hoping to confirm and be able to replace with a reasonably priced rebuilt, the Lexus dealer wants $110 just to look at it.

    Any other suggestions would be welcomed, thanks


  • Mike Gray May 09, 2009

    Hello again, if I understand what you are asking me to do is to find the non battery end of the positive cable and try and directly connect to it. I will try but the Lexus engine leaves little room for maneuvering and if I recall there are a couple of different cables coming from the positive connector. I will try and report back

  • Mike Gray May 09, 2009

    Update 7:30 PDT

    I was unable to easily access the point of the post-ive cable hitting the end point somewhere in the engine compartment. But what I was able to do is connect the positive terminal to the battery and the negative to the engine block (hard to find a good lace to connect) and was able to get interior lights and the engine did turn over on the battery alone. So that tells me that either the negative connection is bad or this is a continuing indictment of the alternator.

    Comments would be appreciated


  • Mike Gray May 09, 2009

    Thanks for taking the time with me on this. It was a trial and error process so ican minimize the repair costs and foucs on the problem


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It is a bad connection some where, and jumping is overpowering it, when jumping do any of the cables get hot?

Try bypassing the cables using jumper cables.
Connect the black cable from the NEG Post to the engine block.
Connect the red cable from the POS Post to the point in which it connects (Starter or Power Point).
This should tell you quickly whether or not it is a cable.
If the cables check out, next step would to test the Charging, voltage should be 13.5 to 14.5 volts with engine running.
If this check out, then you need to check the major fuses, usually in the power distrubution box. Check also the connection on the power buss for the power box.

Posted on May 08, 2009

  • 2 more comments 
  • Ed
    Ed May 09, 2009

    But did you try to start the car with it's own battery, just bypassing the cables using the jumpers?

    it could be a bad ground strap, or a loose connection on the red power wire.

    And yes a meter is worth it weight in gold on these jobs.

  • Ed
    Ed May 09, 2009

    Most large auto parts stores have testers and will generally test for free.

  • Ed
    Ed May 09, 2009

    If you connect the cars battery as you normally would and the car will not start, Correct.

    Now just take the one jumper and connect the NEG Post of the battery to the engine, if the car starts, then the ground strap needs to be replaced.

  • Ed
    Ed May 09, 2009

    As well as the main ******** the battery , there should be some from the engine to chassis, so you can also try you jumper from the chassis to engine and see if it starts.



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The alternator is charged by the battery and provides the supply to the lights, horn, panels, starter, etc. So, if a alternator blows then a person face these kind of issues. Check for the alternator by pulling the spark plug wires one by one of the coil pack and look if it sparks when u start. It takes a second person and dont do it too long, these sparks might wanna find its way fastest to other metal.
No spark means a bad alternator. And regarding the sparks on new battery, it can happen if the wire you are using is cut or loose, Check with a new wire.

Please do accept this solution and revert for further assistance.


Posted on May 08, 2009

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Vehicles: any failing to keep its battery charged.

A vehicle unable to charge its own battery has one of 4 problems:
(a) alternator failure
(b) voltage regulator failure
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(d) wiring problem between battery and alternator/voltage regulator.

One most modern vehicles (including 2002 Lexus RX300 - 2WD and AWD), the voltage regulator is an integral component of the alternator and is not separately serviceable.

In the US, one can get a free "charging system diagnosis" from the popular auto parts chains: AutoZone, Advance Auto Parts & Pep Boys. You needn't remove any parts from the car to get this diagnostic, since they can attach a diagnostic meter to the charging system in the parking lot. This diagnostic aid will tell you exactly which component has failed - battery, alternator or voltage regulator.

In case the vehicle is immobile, one can DIY (do it yourself) the diagnosis.
(a) inspect the wiring for corrosion/loose connections/loose connectors/etc.
(b) check alternator belt/pulley - if drive belt is properly turning the alternator pulley (no slippage/misrouting/etc.), then the mechanical tests are complete, and you'll need to continue testing the electrical performance of the charging system components.
(c) first component to test: battery
DIY test 1: remove battery from car and put battery on a 120VAC automotive battery charger and charge it fully (or just check it in the car with motor off, since the car's charging system is a type of automotive battery charger).
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DIY test 2: disassemble battery out of car after driving it to one of the auto parts chain stores (Advance/AutoZone/Pep Boys) for a free battery test. These testers will test the battery under load, which is not possible with just a DMM.
(d) if wiring is good, and battery tests good under load, then
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(e) DIY test 3: direct alternator/voltage regulator test (car must start and idle successfully to perform this test)
Start the car, and put a VOM/DMM across the terminals of the battery. Since the car is running, you'll be reading the output voltage of the alternator and not the output voltage of the battery. The acceptable ranges for alternator/voltage regulator output are:


Most alternators that are charging properly should produce a voltage of about 13.8 to 14.2 volts at idle with the lights and accessories off. Always refer to the vehicle manufacturer's specifications. Many Asian vehicles, for example, have higher charging voltages of around 15 volts.

When the engine is first started, the charging voltage should rise quickly to about two volts above base battery voltage, then taper off, leveling out at the specified voltage.

The exact charging voltage will vary according to the battery's state of charge, the load on the vehicle's electrical system, and temperature. The lower the temperature the higher the charging voltage, and the higher the temperature the lower the charging voltage. The "normal" charging voltage on a typical application might be 13.9 to 15.1 volts at 77 degrees F. But at 20 degrees F. below zero, the charging voltage might be 14.9 to 15.8 volts. On a hot engine on a hot day, the normal charging voltage might drop to 13.5 to 14.3 volts.

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Note: the VIN 8th digit should be "F" for the 2002 Lexus RX300 (2WD & AWD)

2002 Lexus RX300 (2WD and AWD) - 3.0L Engine, VIN "F" SFI DOHC


Drive belt. Tension the belt to 170-180 lbs. for a new belt or 95-135 lbs. for a used belt.
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Glossary of acronyms
DIY = do it yourself
DMM = Digital Multimeter
DOHC = Dual Overhead Cam
SFI = Sequential Fuel Injection
VOM = Volt Ohmmeter

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