How To Diagnose a Lexus Faulty Starter


Recently my buddy called me sometime in the evening hours and asking me to order him a starter.  I told him, WAIT!  How do you know its the starter that is going bad?  He couldn’t answer me.  I was not trying to put him on the spot, but I didn’t want him to waste 6 hours with $300 plus and find out its not the starter problem.

I tried to coach him via phone, but I don’t think my message was clear enough.  Early next morning I stopped by his home and try to diagnose his problem.  Here are some possible diagnoses why your engine is not turning.

Battery and Associated Cables:

It is possible the battery is weak and cause the engine not to turn.  However, if you turn on all the lights and blast all the fans and still having trouble turning the engine, then its most likely its not the battery.  Second thing you can do is to jump the battery and try again.  If jumping the battery doesn’t help, its most likely not battery or cable problem.  If the battery is weak, the starter will still but very weak or slow.  If the battery is really bad, you might hear the click, click, click, click, click sound.

Anti-Deterrent ECU:

This is also possibility especially someone else drive your car.  This is very common if you lend your car to someone.  The symptom of this condition is “No noise or sound at all” when ignition key is turned.  If this is faulty, the symptom will be the complete ignition kill.  Therefore, you will not heard and clicking sound or engine turning at all.  If this is the problem, you can easily reset the Anti-Deterrent by using your key.  Stand out side of the car and close all doors.  Insert the key into the driver side door and turn the key to clockwise and counterclockwise for three four cycles.  Basically, you are lock, unlock for 4 times and this procedure will reset the anti-deterrent ECU.  If this happen to you, its quite scary at first, but the solution is very simple.

Faulty Starter Relay:

The easiest way to find out if the starter relay is bad is to open up the engine bay fuse box.  You can use a flat screwdriver and take out the cover.  Have a friend try to start the car for you.  If you hear a click sound right at the starter relay (Green Color Square Type Relay).  If it click when your friend try to start the car, then the relay is good.  Second thing you can do is to borrow a starter relay from a friend.  If the working relay installed and the engine still not turning, then its not faulty relay.

Neutral Start:

Believe it or not, the transmission shifter play a role in starting your car too.  As your car aged, the transmission shifter linkage doesn’t give good contact to the starting system and your engine will not turn or click at all.  Here some signs of this problem.

  1. No P (park) or N (Neutral) indicator light while key on.  Even with P & N indicator lights come on but that still doesn’t it has good contact.
  2. When you turn on the key, you should not hear anything at all.  Its a complete silent.  No turning or clicking at all.

To test this out, the best way is to your left hand and push forward on the shifter until you see P while trying to start the car.  Or you can turn the key into on position and hold it there while pushing on the transmission shifter.  Remember this is a very common problem with older cars.

Bypass Starter Circuit:

There are many reasons why the engine won’t turn.  It is possible the circuitry might be faulty.  However, you can test your starter without taking it out.  You can bypass the circuitry and use a positive (+) into the fuse box.  Here are the procedures:

  1. Open up the fuse box with a flat screwdriver.  The fuse box is located near the battery.
    2. Use a 10 mm socket and loose the fuse/relay module.
    3. From there you need to use the same 10 mm socket and loose the plug.
    3. Once the plug is out, look for a large black wire right under the Green Relay (Starter Relay) See starter diagram below.
    4. Supply the black wire with a power source.  Please be careful do not touch this hot wire to anywhere else.


This is a typical picture of a LS400. SC400 is very similar too.
Use a flat screw driver and loosen the bolts.
This is how it looks like when the cover is removed. Use a 10 mm socket and loosen those two 10 mm bolts.
The green relay is the starter relay.
Loosen the bolts and the whole module comes out.
Turn the module upsidedown and use the same 10 mm socket to unbolt the plug.
Once the unplug, you will see the starter relay wire as marked by the red arrow.
This is how you bypass the electronic circuitry.
The opposite side of the bypass plug is the back wire as marked in the picture.

When you supply power to the black (a large black wire right under the green relay) wire, you are pretty much bypassing ECU, relay and connectors.  If your starter is good, it should turn.  Then the problem might be somewhere before the wire or the starter.  If it doesn’t turn, then the starter is almost 100% faulty.  You might hear a click sound but doesn’t turn.  This means the starter is engaging into the flexplate, but not turning.  You might hear only one click sound and that is it.  If bypassing didn’t cause the starter to turn, then its time to spend the money and time to replace the starter.

I believe this is the easiest way to find out if the starter is bad or not without taking the starter out.

Faulty starter is rare, but due to the aging  process, its very common problem for the first generation 1UZFE cars.  This article is intended to rule out starter problem.  Its much easier to change other parts associated with starter, then changing the starter itself.

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This is a freelance site with no support by huge companies.  I have been doing most of the R&D and technical write-ups by myself with my personal money and literally thousands of hours of my time.  I have taken extra steps to demonstrate in details how things are done.  Currently I am one of the few people doing Lexus V8 research and performance enhancement.  This effort comes from my personal love for this wonderful engine.  Most of the modifications are from trill and errors.  There is no cookbook for the 1UZFE modifications and its a virgin territory for performance.  The parts, labor, web development and site hosting are from my personal hobby money.  If you feel my efforts help you in any form, please do not hesitate to donate any amount of money to support this site. You have no idea how much I appreciate it!

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