2012 Prius V wagon. 354k - Replaced passenger side headlight bulb with 100w H11 generic from Amazon. - Bulb soon failed with evidence of burning around base, as well as "welding" itself to connector. - Mechanic had to replace connector by splicing and crimping into existing wiring harness. - Car now will occasionally throw a bunch of lights on dash. Scan for code, no code stored. Clear code anyways to turn off extra lights on dash. - Car will also now turn off ECO mode, which I always leave on. In short, I know my car and how it normally operates. Is it reasonable to conclude given the electrical systems in a Prius V, that any electrical modification will cause all kinds of potential related chaos? I'm guessing, yes! - Had a similar issue recently with spliced wires for an aftermarket fan. What a nightmare. Issue solved when replaced with OEM. - In other words, these cars are highly sensitive to splicing of wires. I'm convinced that my only solution is to replace entire headlight wiring harness with the OEM part. Thought/opinions are welcomed. Thank you!
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).
