Headlights won't turn off, even with the car off.

Just an update: I paid for two days and downloaded the wiring diagrams. Looking through them I see a potential sneak circuit through the Body ECU that could be causing the horn problem, and I see a number of other places where the Body ECU happens to show up in connection with the ABS and Brake circuitry. I can't see a connection that would cause the Brake system to not be working, but it seems like the Body ECU is a black box that might be worth replacing. I ordered a used one off of ebay, and I'll see if replacing it solves any problems.

Looks like a royal pain to get in and replace though. If anyone has replaced one before and knows a sequence of how to take apart the dash, I'd appreciate it. Looks like I should start with the steering wheel, and column cover.

 

I have Volume 1 and 2. Ticks me off that for all that money it doesn't come with the wiring diagrams. I looked through the Body Electrical troubleshooting chart, and there was nothing that matched the symptoms I'm having. It took a look through the wiring diagram to see where the connection between the horn and the Body ECU appear to be.

I'm hoping I can replace the Body ECU without removing the entire dashboard. I see a lot of references that say it is "integral" to the fuse box. I wonder if it can be replaced by itself or if I have to take out the whole fusebox.

 

Well, I just replaced the Body ECU, and it solved exactly one problem: Now I can install the fuse for the horn, and the horn doesn't blow continuously, even when the car is off. It does beep once, when the car is first started (at the same time that the windshield wipers twitch or go through one cycle. I need to go back and look through the diagrams, because somewhere I saw the word "horns" and I assumed it was a misprint. From what I remember seeing in the diagram, there is only one horn. But right now if I hit the horn button on the steering wheel with the fuse out, it makes a smaller beep, and with the fuse in, it makes a louder beep with a dual tone.

As for the rest of it, the voltage at the battery is currently 11.9 with the car "ready" and 12. 6 with the car off. The SRS light, the Brake light, and the ABS light are all still on.

 

(edit: Started response to Patrick, Chap posted before I finished ) Nope. I'm poring over the wiring diagram trying to figure out how it all fits together. Actually, power for the cigarette lighter should be off when the ACC relay is off, so it should be an open circuit, not 810Ω.

The wiring diagram shows a fuse called "cig" which powers the cigarette lighter off the acc relay, which gets its power from the white wire from the 100A DC/DC fusible link, terminal B. Everything leads back to that fuse, but it looks like I have to remove the whole junction box to figure out if that's it or not. It would be nice if I could just pull the fuse and check it.

I spent some time today trying to get the junction box out so I could check it, (I got cocky because removing the dashboard fusebox was much easier than I expected). But it looks like the only way the junction box will come out is if I remove the inverter.

 

Posted here for reference: 100 Amp Fuse Replacement | PriusChat

 

I'm copying these instructions from the other thread. Can anyone guess what he's talking about when he says the "aquarium cover?"

1. Disconnect the positive lead for the auxilliary battery.

2. Remove the funnel attachment for the wiper fluid reservoir.

3. Disconnect the 5 electrical connecters (each is unique so no worries when re-assembling) to the left of the fuse box. Pull that bundle back and undo the tie to the fusebox and the first two ties on the aquarium cover.

4. Remove at least 1 screw from the bracket holding the bundle connectors that run under the electric motor housing cover. You probably can't get to the second one anyway. I couldn't. Push the bracket down and to the left as much as possible.

5. Remove the 2 x 10MM bolts that secure the fusebox to the body. I needed a wobbly bar and a 90 degree adapter for the rear one.

6. Unclip the highside A/C line from the front ground cable and aquarium cover and move it to the left a couple inches. Take care not to kink the line. That would be bad.

7. Using a flathead screwdriver, unclip the 4 clips (1 on each side) that hold the bottom cover of the fusebox to the top and wiggle the bottom out from underneath. There is a cutout so that it goes around the bundles running into the box.

8. Use a flathead screwdriver to push in the two clips that hold the fusible link connector block to the fusebox. Slide it out the bottom of the fusebox. Move the main fusebox as far forward as possible.

9. Disconnect the black connector on the bottom of the link block.

10. Pry back the 4 arrowhead shaped retainer clips on the longer sides of the fusible link block. Slide the lighter colored covers down, revealing the retaining bolts (4 total) for the link and cables.

11. Loosen the 10MM bolt holding the link on the right side. Loosen the 8MM bolt holding the link on the left side. Pull out the blown 100A link. You do not need to remove the other 2 bolts.

12. Replacement is reverse of removal.

13. Check the rest of your fuses. I had 4 blown 10A and 15A fuses from the original overload. All minor stuff, but blown is blown.

Read more: http://priuschat.com/threads/100-amp-fuse-replacement.25244/#ixzz2qQgXDIxM
Follow us: @PriusChat on Twitter | PriusChat on Facebook​

 

I figured I should post a progress report. I replaced the 100 amp dc/dc fuse some time ago, and most of the car is back to normal. I still have the brake/abs lights on the dash, and as far as I can tell, it means that I am using plain old fashioned hydraulic brakes, which is just fine with me. The only problem is that it probably doesn't pass inspection. I'm thinking of removing the bulbs so the inspectors can't tell there's anything wrong.

 

Oh, and for any one reading this who needs to replace the 100 amp fuse, I spent a lot of time trying to figure out how the wire got shortened, because it fit one of the connectors on the bottom of the fuse box, but there was no way it could reach with the fuse box in place. It turned out that the connector on the fuse box just isn't used, and the cable plugs into the bottom of the white plastic fuse carrier thingy. I didn't even realize that it had been plugged in there, because I couldn't see what I was unplugging.

Once I figured out that there was a plug down there, it wasn't that hard to put it all back together.

If I had it all to do again, I wish someone had told me if you release the 100 amp fuse carrier and lift the fusebox up to disconnect the connectors underneath it, leave the fuse carrier alone until you've got the entire fusebox out of the car. It will make much more sense to put it back together that way.

 

My first reaction was to dismiss the suggestion, because I'm quite sure that there is an electrical issue involved. Then I figured that denial wasn't a valid response, so I checked the fluid.

It's right between the Low and High marks.

 

It would help if I new what Tc and GC was.