Splicing Headlight Wiring Connector Issues

If you have aftermarket LED bulbs in those sockets they can cause interference.

 

There are led bulbs with built in filters and there are plug in filters as well. The splices on those circuits (eg non-comm) are not the issue.

 

I would examine the mechanics work first.

The wires are of a very small gauge.

If he or she used crimped connectors the connector may have high resistance and causes a fault and a voltage drop.

In this case, solder connections covered with heat shrink tubing is a much better long lasting option.

 

A 100w halogen lamp capsule could easily melt the lamp holder base if not also the wiring, especially if corrosion was present.

 

This is a FPS (frequently-posted situation) on PriusChat, because there are so many code scanners out there that don't show all the codes from a Prius. If there are warning lights on and the scanner you're using won't show you the codes that tell you why, a better scan tool is needed for the next time the lights come on.

That would be too much to conclude on the evidence you've supplied. You've been getting some trouble code or codes starting after the work was done, and because of the scan tool you're using, you don't know what code(s) yet. The likeliest situation is that the codes are being set because their normal detection conditions have been triggered and they mean what they normally mean, and that finding out what codes they are will get you valuable clues into the situation. The fact that you don't yet know what the codes are does not, by itself, turn the situation into "chaos".

I haven't noticed them to be any more finicky than anything else in that respect. But see below about headlight splicing specifically

You're in for some sticker shock with that approach. Unless they wired the v radically differently from the gen 3 liftback, there is no separate "headlight wiring harness" for you to replace. Those circuits are part of the Engine Room Main wire harness, which runs throughout the engine bay, includes the fuse box, penetrates the firewall in two places, and connects to other items and harnesses at multiple locations accessed by removing the dash top. On top of the price of the harness itself, it's a laborious replacement.

Caution: the link I gave above is to a part number for a 2012 v engine room main harness. But there are probably several different part numbers for that depending on the car's exact trim and options. If you choose to go that route, you need to be very careful to get the exact right one.

Careful when splicing gen 3 headlight wires:

Although I'm not in the "car is super finicky, mods will cause chaos" camp, I still do recommend checking the mechanic's splicing work very carefully and being prepared to redo it.

That's for a whole different reason: if the v is like the gen 3 liftback, Toyota used aluminum wiring there.



There are very specific instructions and materials for splicing to aluminum wiring. Improper copper-to-aluminum splicing was a notorious factor in house fires in ~ 1970s USA.

You can read more about that issue in the gen 3 harness here and here (and in the posts that follow those).

 

Don't know about aluminum wiring.

I have soldered a lot of Toyota wiring and found that it is copper and solders just fine.

 

Most of it is.

So that's why when they go out of their way to alert you to a specific circuit being aluminum and give you training material on how to splice it safely, that counts as new information worth paying attention to.

 

Only, I don't think that the wires are aluminum unless they have a copper outer coating.

Small gauge wires need to be of heavier gauge to carry the same amperage of current. Stranded wires, if coated with an outer layer of copper would have the same "halo" effect as solid copper strands.

Unless you provide proof, I don't see any advantage for using small gauge aluminum wiring.

Aluminum for heavy high voltage long distance transmission lines us another matter.

 

There are a few kinds of 'proof' one could 'provide' here.

As far as 'proof' that there's "any advantage" to Toyota using aluminum anywhere in their harnesses, I don't think I'm the person to ask. I trust that discussion took place among Toyota engineers, or they wouldn't be using aluminum in their harnesses.

As far as 'proof' that they do use aluminum anywhere in their harnesses, to me it is proof enough that they say so, on page 138 of the training course book for their T623 Electrical Circuit Diagnosis course (available under the "Technical Training" tab on techinfo), from which I took the illustration and caution that you see above in post #9.

As far as 'proof' that the gen 3 low-beam headlight circuit (at the very least in 2010–11 liftbacks, which were the cars covered by T-SB-0204-12) might be one circuit where they used Al, to me it is proof enough that the splicing instructions in that TSB expressly specify the crimp tool 09042-2C100 and crimp sleeve 82999-52010, exactly as specified in their training literature for splices to aluminum (and different from the tool and sleeves specified for non-aluminum splices), and that the low-beam circuit's insulation looks like the color they use to distinguish circuits using aluminum (see, again, post #9 upthread).

I'm not aware of any other case where they've specified those Cu-Al-specific crimp sleeves and tool for non-CuAl splicing. I suppose the sleeve and tool would make a perfectly serviceable Cu-Cu connection, but Toyota specifies their other, more common, sleeves and tool for that.

So, absent some goofier explanation (could the person assigned to write T-SB-0204-12 have looked at the insulation color and thought "that's the color we've been using for Al wire, so I need to specify the Al-specific crimp sleeve and tool" when it's really just a Cu wire with that color code by chance?), the most straightforward interpretation points to Al being used there.