flash9

After doing the work to replace my Spark Plugs and Wires as well as the Valve Cover Gaskets, I noticed that the Battery Light on my dash was not going off once I started the car.

Looking a little closer I noticed that the “3” white with green stripe wire to the plastic connector to the alternator (Lexus calls it a generator) had broken. A little research shows this connector plugs into the alternators IC (Voltage) Regulator. I was able to solder the wire back onto the metal clip, but while removing the metal clip from the plastic plug/connector, it basically cracked and disintegrated. I found a replacement plastic clip on Amazon and swapped over the three metal clips to the new alternator connector clip.


The New IC (Voltage) Regulator Clip


#3 Wire that was broken.

I was thinking this would make the Battery Light go off, but no luck. I thought that maybe this would be a fault/error in the OBD system that I could RESET, but neither my OBD reader, nor the Lexus TIS Techstream found any errors, and in fact does not even seem to monitor the Battery or Alternator.

I drove the car to the local Advanced Auto and they connected a battery/generator tester. The Battery Tested GOOD, then the alternator tested GOOD both Under Load and Not Under Load.


Advanced Auto Parts - Battery, Starter, and Alternator Test Report

So, this tells me the Battery is fine and the Alternator and its IC Regulator are fine, and it points back to one of the following:

• The three wire plug connection to the IC Regulator is not making contact
• One or more of the three wires in the wiring harness is broken
• I forgot to plug something back together when putting everything back together

I found the following wiring diagram of the Charging System.


2003 Lexus GS300 Charging System Wiring Diagram
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• Will this “reset” itself given enough time/mileage?
• Am I missing something in the Lexus TIS Techstream, and can I “reset” the Battery Light?
• Is there any connections that these three wires connected to the IC Regulator go to, that maybe I forgot to clip back together?
• Is there a way to test the three wires that leave the IC Regulator connection?
• Is there something else that could be making the Battery Light stay lit?

KTGS300

Why not just test the 3 wires for continuity from one side of the wire harness to the other with a DMM?

sbagdon

I would have gotten a used oem plug from the salvage yard, rather then risking using a non-oem part... we've had terrible luck with plastic parts that aren't oem, in regards to fit/finish.

At that point, get the plug working with oem, validate the harness positions, then start by testing the cold and running voltage.

flash9

I had thought of that, and I can follow these wires to this "T".


I suspect they go to the RIGHT, but even if I confirmed that I have no idea where they end up and if there is plug/connector I could open to test the continuity.



The wiring diagram clearly shows each of these three wires heading off to three different connections.
I circled each connector for each wire.
Can anyone point me to where I should look for each of these connection locations?
Also, where is the 5A Fuse I circled in GREEN located? Is it under the hood or on the passenger foot-well location of fuses?

flash9

I looked in the Owners Manual and found the 5A Fuse in this Fuse Panel Under the Hood just in front of the battery.
My guess is this must have blown when the wire broke and shorted out somehow.


Maybe this will help someone else in the future.
I started the car and sure enough the Battery Light went OFF!

pvallest

SOLVED! I had the exact same experience you did down the valve cover gaskets and all. Thanks for taking the time to document your fix so well and sharing. I knew there had to be a fuse blown somewhere but hadn't found it yet when I searched and found your post.

flash9

Glad this was of help - I did this repair in May of last year, and I can barely remember any of this.