Long read: My 2009 Prius HID headlight odyssey

2009 Toyota Prius Gen II. Purchased second hand in 2015. New user here and writing this up so it might be able to help other folks who are having the terrible issues I had with replacing a Prius HID headlight.


This all started about six months ago. I had the front passenger headlight go completely out on my Prius. So I stroll into my local Autozone and buy a $10 halogen bulb. I crack open the hood and, holy shit how do you actually get to this headlight? Mess around under the hood with some neighbors and discover that you have to remove part of the engine cover and the front bumper to loosen up the headlight enclosure then remove 10mm screws on top. Just to get to the wiring harnesses at the headlight enclosure.


Ok. Undo the clip that retains the bulb in there and...dammit this isn’t the right bulb. It’s then that I discover I have HID headlights. Extract HID bulb and bring it back to Autozone to get a new one and holy shit are these things expensive (I later learned to buy online). Part matches--my Toyota manual says to get a D4R HID bulb.

I stick the thing in there and I have light!


Except not. I went from having nothing to having a light that turns on for 30 seconds. (Hindsight alert: I should have suspected something with the bulb then and there). This is bad...but I got the right bulb? I do some research and discover that Toyota really effed up on the headlights with the Gen II Prius. Dozens of pages of forums with people reporting their issues with HID lights. Dig a little deeper and learn about the issue these Priuses (Prii?) have with the HID ballast. Apparently moisture gets in there and fries this little computer that controls how the ballast works resulting in a light that will die after a short amount of time and must continuously be switched on and off to reignite. Find an aftermarket retailer online and purchase a new ballast that fits my year.


(Hindsight alert 2: I should have tried switching the bulbs and seeing if the 30 second outage issue happens on both sides--would have been able to determine if its the ballast or then and there).


OK. Getting to the ballast which is inside the light is just awful. I luckily had my uncle and his fabulous garage to help me with this but the gist is:

1. Remove headlight enclosure completely
   
   
2. Unscrew ballast
   
   
3. Perform wacky surgery on ballast since its connectors were poorly designed and have to be cracked open/spliced so that its cables can snake back through the headlight connector (for a better idea of this, there’s this video:
   )
   
   
4. Reconnect everything and try out your newly fixed ballast.

Except not. We get past step 2 and, uh-oh, the part I bought doesn’t look like it will fit. But but, I have a 2009 Prius! I have the piece the guy in video has--a squarish black ballast. Uncle and I crack open the headlight and my ballast is rectangular. It’s just not going to fit. (Hindsight alert 3: I should have known not to trust anything but what I see in my car at that point.) I’m starting to have serious doubts that I even have a 2009 at this point. But I check against my VIN and my 10th digit is a nine which confirms it as such. Take a picture of the (bad) ballast that’s in there. And it looks like this (the circle is mine and will be critical info later).





But I don’t give up. Back to the aftermarket site. Find the more rectangular headlight. Back to my Uncle’s garage with new headlight (I’m into this fix for $150 at this point, Toyota can charge up to $600 to fix these according to online forums so still worth it. Also worth mentioning, Toyota had to settle a class action about this a few years ago but I was beyond the time frame to get mine fixed--I think? If anyone has experience with this part, do share).


Alright so old one out, new one in. I’m making that sound way easier than it was. It sucked honestly. But we plug the new one in there. Annnddd….drumroll….


With the new ballast the same headlight goes out after 30 seconds.


OK. Extremely annoyed now. Ready to drive car into the ocean. But uncle talks me off the ledge: I had no headlight, got a replacement, then only had 35 seconds. But before the headlight went out I didn’t have the 35 second issue. Could it be the bulb? He suggests I try switching the bulbs. If the problem travels with the bulb--its the bulb. Maybe its that the new bulb is drawing too much power and it’s causing a circuit breaker to trip after 35 seconds, he says.

Maybe I got a hot bulb or something. Check the driver’s manual again: D4R bulb. Check online part sites: they warn heavily that any other type of HID bulb that is not the D4R will not fit my 2009 Toyota Prius. Even called a Toyota Dealer’s Parts Department and gave them my VIN and they said D4R (quoted me at $150 for the bulb, ha). Anyway, time to try swapping the bulb. I have enough experience after failing to fix this twice that by now I can do this on my own. I first remove the good light and take a good look at it.

Huh. D2R. Not D4R. Even though my manual says D4R. Even though everything online says D2R bulbs will not fit your 2009 Toyota Prius. Swap the bulbs--the opposite headlight has the 35 second issue now. Now take a look back at that ballast picture. It says D2R right on there. I was still in the dark (literally) about it possibly being the bulb and ignored that info. Buy D2R bulb off Amazon, get it two days later, put it in in place for the bad one, and now I have two working headlights.


Not sure of exactly what the difference between D2R and D4R is but I believe one has mercury and one doesn’t and the energy consumption difference is what was tripping a circuit breaker. I guess I have a completely different style of HID headlight that is an aberration for its year also? I suppose I’m not pissed about replacing the ballast. Those things do fail and now I have a new one. But that whole fix ended up being a massive red herring. This is what probably happened: Autozone guy checks computer for what type of HID headlight is for a 2009 Prius and he sees D4R and that’s what I put and that’s what starts my 35 second issue that I mistook for being the ballast. I don’t blame the guy, my DRIVER’S MANUAL says to get the D4R. I did bring him in the old bad D2R when I first bought it but still ended up with the wrong part. Maybe if you’re not really looking you can assume they’re the same.


Here’s the moral of the story, I guess: observe the bad thing about your vehicle first hand. Do not read online stuff (including this post!) or even trust what a Toyota dealer says. Also think about when the issue started happening and think about if anything in the car changed around that time.


Thanks to my uncle for helping me do this whole thing and also providing the clue that eventually got it working. Anyway, thanks for reading. Good luck Prius owners.