Warning lights activated after connecting to a boat trailer and repairing the boat trailer's lights

Tiny
FXD5CC
  • MEMBER
  • 2012 TOYOTA HIGHLANDER
  • 3.7L
  • V6
  • 4WD
  • AUTOMATIC
  • 133,000 MILES
Parked vehicle next to a boat trailer to connect and repair faulty trailer lights for season. Finished the repair and unhooked boat trailer and started car to leave ABS and Master Alarms activated, Transmission locked. There were no brake issues prior to this and the car runs perfectly. The brakes seem nearly new, rotors great, etc.
Something happened while I hooked the trailer up.
Short? Fuse? Relay?
Can I reset the computer to clear these?
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Sunday, June 19th, 2022 AT 7:34 AM

3 Replies

Tiny
AL514
  • EXPERT
Hello, if you have the ABS light come on, there should be a diagnostic trouble code stored in the ABS module (computer), so don't erase anything because it will be the only information you will have right now as to what may have happened. Erasing the memory or codes might restore its function, but we will have no idea where to start checking. You won't be able to scan the ABS module with a basic scan tool, it will need to be a scan tool that can scan all the modules in the vehicle. Not just the Engine computer. If you can get a full system scan done on the vehicle, there will most likely be some codes to give diagnostic directions. Because this vehicle has traction control and Skid control incorporated into ABS system, you will need to get a scan tool that can scan the ABS, but it would be better to get a full system scan done just in case there are codes stored in other modules that are just not showing a caution light right now such as the Transmission module. Obviously there has been some kind of failure, corrupted data, or communications fault detected. I recommend figuring out what is happening before you attempt to tow anything. You don't want to lose some function especially with a heavy load like that.
These vehicles can have load sensors on the Brake pedal switch, downhill braking assist, steering sensor, yaw rate sensor, etc. So, it most likely was something to do with the load you were trying to tow that triggered a code. Interesting that the transmission locked up, that might be a security type activation as well.
I don't see any technical service bulletins on anything like this either.
You can start by checking these fuses, just don't pull any out, because it may erase codes stored in the engine computer which looks like it also controls the Transmission. I would just check these with an Automotive 12v test light hooked to battery negative, if they are Maxi fuses you can see into them and see if they are blown.
And have you had any work done lately, even just tires changed?
One other thing, is there an Information Display in your vehicle and if so, is there anything besides a master alarm and ABS light?

After taking a look at the wiring diagrams here are a few other fuses to check, and what kind of repair did you need to do to the trailer lights assembly?
Fuses to check FL Main, ALT 140amp, TAIL 15amp, ECU IG 7.5amp, STOP 10amp, TOWING 30amp.
The FL MAIN is a fusible link located near the battery, these are not regular fuses, it is a section of wire that is designed to burn just like a fuse when there is excessive current flow. This one appears to be hooked directly to the battery (5th diagram).

https://www.2carpros.com/articles/anti-lock-system-testing-and-repair-abs
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Sunday, June 19th, 2022 AT 10:43 AM
Tiny
FXD5CC
  • MEMBER
Sorry, I'm not considering towing the boat until the issue is corrected. Like most older trailers every spring you fix light connections, bulbs etc, etc. The brake lights are not working, everything else had a workaround and the ABS alarm locks the shifter in park on these SUV's. You would think AutoZone folks would know their scanner won't read ABS codes.
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Sunday, June 19th, 2022 AT 11:26 AM
Tiny
AL514
  • EXPERT
Yeah, the AutoZone and Advanced Auto are not technicians, but a short circuit in the Towing Converter for the exterior lights may have burned any of those fuses. I'll put the diagram below, but the Towing Converter has a lighting trailer connector running through it. It's also incorporated into the Skid ECU which controls the ABS system and Traction control. So, if it blew a fuse while you were doing your electrical checks, that would explain why it happened after you unhooked everything and started the vehicle to move it.
Diagrams 2 and 3 are the Stop lamp circuit, you can see how it's all integrated with the Skid control unit, Stop Relay, etc., so I think you're going to find a blown fuse here. Hopefully that's all. With all these fuses it looks like a pretty protected circuit,
You're going to have to check the fuses under the hood and on the driver side dash Instrument Panel Junction Box. If you find a blown fuse, let me know what fuse it is and maybe we can narrow down a short circuit without you having to go through too much trouble. I'll look up where this Towing Converter is located.
The fourth diagram is the Towing Converter under the driver side dash, you'll have to locate it by the wire coloring.
The fifth diagram is the actually wiring itself. The converter combines the Turn Signal and Brake light lamps together and switches the brake lamp off when the turn signal is on, if you only have one lamp per side for the turn/stop lamps. But you might want to check the wiring to make sure there isn't any obvious shorts to ground. The white/black wire on the trailer hitch end plug is the Ground, yellow looks like Left Turn Stop lamp and green is the Right Turn Stop lamp. There are two connectors back there AN1 and NO1, it also looks like the ground might be a shielded circuit back there and due to vibrations and regular driving those wires can short out any place it's close to the frame.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

https://www.2carpros.com/articles/how-to-check-a-car-fuse
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Sunday, June 19th, 2022 AT 11:37 AM

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