2004 GX470 147K

Brake, ABS, VSC Trac, VSC Off lights are always lit.

Brakes seem to work just fine, firm, no fade. Mechanic checked out the car and replaced fluids and said he felt it was good to drive, but that some sensor had failed. He didnt have the manual to figure it out. There are no codes stored, so I disconnected battery to clear memory, reconnected, lights come on immediately at startup. Hooked up my scanner and it didn't reveal any culprit. Driving around didnt affect them in the slightest.

What are the common culprits that will cause it and trigger immediately at startup, it must be a sensor of some type but need to know the troubleshooting procedure. Is there a factory shop manual online?

 

Two common causes:
- Old/worn gas cap. P/N is 77300-33070
- Blown ECU-B fuse

Chip H.

 

Checked the fuse, the fuse is still good. Gas cap was tight and made sure it clicked a few times.

 

I had the same problem. Even if the gas cap seems to fit tightly it still may not be sealing correctly. In my case, a new Toyota cap fixed my GX right up.

I have no idea why Toyota / Lexus thought it would be a good idea to illuminate brake system warning lights for this issue

 

Assuming the cap is good what else are likely causes?

 

Replace the cap first. Really.

If you want the shop manual, Toyota has a copy online, and charges $20 for a couple of days access: techinfo.toyota.com
(hint: make screenshots)

Chip H.

 

If the cap gasket is hardened it's time for a change. Easy enough to check. You can buy the gasket from Toyota, about $10 as I recall. My warning lights had to be reset by disconnecting the battery.

 

Gas cap replaced, lights still come on immediately at startup. Should a scanner be pulling out ABS codes from the computer that would tell which sensor has failed?

 

OK, now is the time to dig deeper.
You'll want a Toyota/Lexus specific code reader (although a really good 3rd party reader might be able get codes from the braking system).
Find a independent Toyota specialist, or pay the dealer their (steep) diagnostic fee.

Chip H.

 

Specific Lexus/Toyota reader is not required, just a reader capable of ABS code reading.

Code indicated faulty RR wheel speed sensor. Fairly simple to replace once you get to it.

 

I just resolved my issue with the same warning lights (Brake, ABS, VSC Trac, VSC Off lights) on a 2004 GX470. My codes were C0200, C0205, C1223 and C1224, got the codes from auto part store, which indicate issue with both the Front Driver and Passenger side wheel speed sensors. I resolve the issue myself, I started by measuring the resistance on both speed sensors at the wheels by disconnecting the wires harness and using a multi-meter to read the resistance. Both wheel speed sensors had resistance of around 5K, so then i reconnect the wire harness and measure the resistance from the wire harness which show open circuit on both wire harnesses. Ordered the wire harnesses from Lexus (8951660070 and 8951660080) and replace these wire harnesses which automatically clear all the codes. Note: a lot easier to replace the wire harnesses by removing both front wheels first to easily access the wire harnesses.

 

Just adding to this. I had the same issue (lights on, no codes), and all that needed to was use some sensor clean on the ABS sensor connectors. Hope this helps some of you.

 

Why was there open ckt wires, and for both sides? What you describe sounds more like bad connectors and not bad wiring.