WA: Lexus GX470 ABS - VSC TRAC - VSC OFF lights on with beeping

[LTunedX]

As the title states, please read:
Bone stock 03 GX currently at 155,000 miles. We bought this truck in 2022 with 120K miles. No problems until...

09/23/2025: Camping on Whidbey Island, WA. 50-60 degree F temps. Woke up and went out to the truck, then with the key in the ON position (normal/usual fuel prime for a few seconds before starting engine)

The ABS - VSC TRAC - and VSC OFF lights come on followed by the steady beep... first time since buying the truck has anything happened.

Quick search lead to a quick battery check, so I hooked up a battery charger. Battery was a little under normal (maybe due to dropping overnight temperatures camping) plus this battery is the one that came with the truck and may have been nearing the end of its usable life - date sticker was peeling/partly ripped.

Quick online searches while the battery charger was hooked up, lead to the potential brake problems... so I did a basic 40-50 brake pedal pump with the engine off to see if it was the pressure.

Fired up the engine, same lights on with beeping... stiff brake pedal but not much traffic so I drove onto a country road...

Range anxiety at this point for how far from home we were and of all things potential brake failure.

ALL LIGHTS and BEEPING went away after driving 35-40 MPH for about a quarter mile to a corner store to double check... lights and beeping did not come back on.

Had a good day at the beach and safely drove 100 miles back to Seattle with full braking power and no problems...

daily drove the truck as usual...

Fast forward to November 8, 2025 - battery died at the store so jumped it with a portable jumper and drove home...

While driving home, same lights and beeping came back and pedal went stiff, but good thing I was only a couple miles from home so floated the rig home extra cautiously...

The truck sat through the holidays and put a new battery in last week... same lights and beeping came on then went away while driving...

Double checked for the ABS box buzz sound and it buzzes... new battery in, lights and beeping off... until now

Same dang lights are back on with the same beeping...

Did the booster just happen to fail?

Have not done ZPC. Previous owner swapped air to standard coil spring, and when I went to check fuses they were all pulled (the 2 in kick panel and the 2 in engine bay)

Truck is completely stock. Only thing it needs is rust repair but might not have anything to do with the current problem...

 

[M3GX]

get a scanner on the ODB and check for error codes. Lately I've been getting a "small evap leak" error and it kicks the VSC lights on for some reason when that happens.

 

[LTunedX]

get a scanner on the ODB and check for error codes. Lately I've been getting a "small evap leak" error and it kicks the VSC lights on for some reason when that happens.

Thanks for the reply, with how this all happened it could be something as simple as your emission type error since the brakes will function normally when all the lights turn off. With the new battery in, resetting it every day or two to check out whatever on the truck, a check engine light last night. Ordered an OBD scanner that checks ABS codes aside from engine CEL and will be delivered Sat 02/14/2026. Not driving the truck anywhere due to stiff pedal as only drives have been the slow 20-25 MPH rolls to check if the lights turn off. As of now while waiting for scanner to be delivered: ABS LIGHT, VSC TRAC, VSC OFF, and now red BRAKE light stays on and a Check Engine Light last night. Will update this post as soon as CEL code and ABS codes are scanned.

 

[Alleycats]

I would say it sounds like the air injection system to me, but I believe your rig predates that? Others will surely chime in.

 

[LTunedX]

I will update this post as soon as I replace all oxygen sensors and gas cap. To be clear, there was no Check Engine Light when this all started. After putting a new battery in clearing the ABS, VSC TRAC, VSC OFF, and steady beeping. Shortly AFTER a new battery, the CEL came on for oxygen sensors. Ordered all new o2's and a new gas cap while at it. Again, there was no CEL from time of purchase in 2022 with 120K miles, no CEL when the three indicators lit up plus beeping in September 2025. Only within these last few weeks has the CEL come on (after new battery which temporarily cancelled out the dash lights & beeping). As of the posting of this reply, red BRAKE light indicator on, ABS, VSC TRAC, and VSC OFF lights on along with the steady beeping is back and a CEL for o2's. Will see what happens after new o2's are in along with gas cap. Thank you for chiming in.

 

[Rednexus]

You'll need to pull all of the codes to diagnose this (normal emissions codes as well as Toyota-specific ABS/VSC codes). If you can pull those and post them that will help.

 

[LTunedX]

As of this posting, the scanner came up with P0031 & P0051 - Oxygen Sensors. When I clicked on Anti-lock Braking System Codes: None stored.

Noted/Reported on the scanner with the o2 sensor codes was "low voltage to oxygen sensors for predetermined period of time." So I hooked a portable jumper up with alternator tester and came up 12.6 steady with engine running, no fluctuating, no decreases, no increases to healthy mid 13's, 14's. Stays at 12.6.

Maybe the weakening battery in September slowly took the alternator with it (or just needs to be replaced)? Mild September temperatures (around 60 degrees when all this started all through November 8 when the battery finally needed a jump) - then new battery/terminals turned all said lights off right away, then came back plus stiff pedal in January maybe slowly lead to this point.

So the CEL for oxygen sensors was only within the last couple of weeks which may be be due to age or "quoted" report of low voltage...

The BRAKE, ABS, VSC lights, and stiff brake pedal may be from the electrical system....

Learning the sensitivities and common fault points of this first generation 2003 GX as I've never owned one before. Will update after sensors are in, and alternator is replaced. This is all productive and informative so far, thank you.