accordfixit

I'm new here, but have been reading for a while now. My problem is not new, but thus far, no solutions have worked. Please bear with me, this could get confusing.

Car: 2000 Honda Accord Coupe

My problem: the left and right brake lights do not light up. The window brake light works just fine. All other tail-light functions work as well, just not the brake lights.

My temporary solution: I cut the power (black/white wire) to the brake lights and wired them to the center brake light. I do not want this to be permanent.

My failed attempts:

-I have new tail light wiring harnesses in case of a bad socket and to fix my temporary solution.

-I checked all fuses/relays

-I checked all grounds

-I checked all wires for breaks or shorts

-I replaced the Brake Light Failure Sensor

-I replaced all bulbs

What I've investigated: I can get 12v of power on the black/white power-in wire to the Brake light failure sensor (BRFS). However, I cannot measure any power coming out via the green wire from the BRFS. The odd thing, is that if I jump the black/white power in to the green power out, I suddenly get no measurable power.

I'm at a loss right now. I will answer any questions as soon as I can, and any answer is appreciated and any advice will be considered! You could tell me to do a rain-dance, and I probably will at this point. Thank you in advance for your answer and for even reading this.

tech8

1. Just to clarify the wiring color first. The power supply (+) coming from the brake light switch is referred to as Wht/Blk instead of Blk/Wht. Wht/Blk is a wire with white colored insulation and a black stripe running through it.

2. If I am understanding this correctly, for your temporary working solution; you've cut the Wht/Blk wire from the left and right brake lights (before the Brake Light Failure Sensor) and connected it to the Wht/Blk wire of the high-mount brake light.

If this is the case, that would mean the ground to the left and right brake lights are okay, and the Brake Light Failure Sensor may be okay.

That would lead me to believe you have a wiring issue with the Wht/Blk wire at the 12P gray connector (Connector C554) in the trunk area. Connector C554 should be on left side of the trunk area, higher up and should be visible somewhere near the left speaker. Power from the brake light switch runs via the Wht/Blk wire, splitting off to the high-mount brake light, and then runs through Connector C554 to the Brake Light Failure Sensor. It sounds like you have an open in the Wht/Blk wire going in or out of Connector C554 and your working solution bypassed the open in the wiring.

accordfixit

Thanks for the reply! Let me clarify my temporary fix.

I cut the white/black wire (power supply) on the left/right tail light harness and spliced the wire from the bulb socket to the center/window brake light.

I can measure a full 12v at the Brake Light Failure Sensor coming from the white/black wire (Referred to in diagrams as the Brake Switch Input). However, I can't measure any power coming out of the BLFS at the green wire (referred to in diagrams as the Brake Light Input). This is troubling since I bought a brand new BLFS from the dealer (Power in but no power out, I figured it was a bad sensor).

I checked the green wire (Brake Light Input) and all grounds for continuity and they all check out. I measured 12v of power at the yellow wire (Ignition Input in diagrams) just to be sure and it's sound as well.

I have diagrams that I can upload, but I'm unsure how. Any advice would be greatly appreciated. Thanks again!

tech8

You may possibly have to have 5 posts before you can add attachments?

I have the diagrams and images; if you attach diagram, add mark-ups, comments to the diagrams.


I am still a little unclear on your temporary fix. Is the green wire from the bulbs bypassing the BLFS and directly connected to the Wht/Blk wire for the high mount brake light?

tech8

Did you check the ground wire connection going to the BLFS?

accordfixit

Ok, I did not cut the green wire. I haven't modified the main wiring harness in the trunk at all.

Each tail light has 2 sockets, 2 dual-filament bulbs, and one connector that connects to the main wiring harness. I modified this smaller harness. On the diagram you posted, it would be the white/black wire coming directly out of the brake light bulb, not the green wire.

Currently, I have replaced the smaller harnesses with new ones, so I completely have stock/factory wiring. My temporary fix is no more, as I'm after a permanent one.

I did check the ground coming out of the BLFS for continuity, and it checked out. I used my multimeter's continuity setting as well as an OHM meter to check for breaks or shorts in each wire, and so far everything checks out. I won't rule out human error, as I'm not a professional in any sense - just too broke to hire someone.

tech8

From the high-mount brake light wht/blk wire, which color wire was this connected to, for the temporary fix?

accordfixit

I connected the white/black wire from the high mount brake light to the white/black wire from the left/right brake lights using some extra wire I had in the garage.

I used a temporary plastic wire splice to clip onto the high mount brake light white/black wire so I wouldn't have to cut it. However, I did cut the white/black wires coming from the left/right bulb sockets and did a more permanent splice on that end.

As I said though, I removed all of this and replaced the tail light wiring with factory new.

tech8

The circuit diagram doesn't show the wht/blk wire going directly to the bulb sockets. It shows it going to the BLFS.

Was your temporary fix wiring like this diagram? If so, the problem sounds like an open in the wiring at connector C554.

accordfixit

OK, I don't have permission to post images yet.. have to wait another 4 days. I can email/PM(?) an edited wiring diagram to show what I did, I just can't post it to the forums yet.

Anyhow, the connection point on the High Mount Brake light is correct in your edit. However, the connection I made at the tail light is within the 'gray' box around the Outer Brake Light/Tail Light on both Left and Right Taillight Assembly. The White/Black wire is what I cut. That wire is connected to the green wire via connector.

So my fix basically bypassed the BLFS as a power source and used the Brake Pedal Position Switch as a power source instead.

Does that make sense? I really wish I could post the image. Oh well..

tech8

Okay, that makes sense now.

Somewhat unusual, even with a new BLFS, for power to not go through. I would be looking at the ground wire from G601 going to the BLFS.

accordfixit

Yeah, this is not the most fun problem I've ever had to try to work on. I will double check the ground coming out of the BLFS for continuity. I think I'll also make sure the GRN wire isn't (somehow?) connecting to a ground.

I'll report back when I check the grounds. Thanks for all your help so far.

accordfixit

Haven't had a chance check the grounds yet. My wife was ill last night, so no opportunity to work on the car.

tech8

What you mentioned about the grn wire being grounded is a possibility too.

accordfixit

OK, so I'm going to retest this just to be sure, but there IS continuity between the GRN wire and Ground. I'm guessing this is why I can't measure any current on it when I jump it to the WHT/BLK wire at the BLFS connector.

Like I said, I'm going to retest this just to make sure I didn't overlook something, but I think this may be the culprit. If so, what would you suggest I do to find the GRN-Ground connection? OR, instead of finding it, should I just cut the GRN wire before the connectors and splice in new wire altogether?

tech8

I would try to find where the grn wire is touching a ground source or a ground wire (wiring or terminal connector).

Try this, disconnect the connectors to the individual inner brake/taillight. Do one side at a time to try to see if it may isolate which side may be an issue (if it is an issue with the wiring at the inner brake light wiring), and see if your outer brake lights work with the inner brake light disconnected. --Disconnecting the inner brake light connector may not necessarily reveal the problem, so test for continuity between the grn wire to ground on both male and female side there too.

accordfixit

Sounds good. I'll do this after work today and report back on what I find.

Thanks again for all your help so far!

accordfixit

Ok, sorry I was gone so long - life has plenty of other problems I'm trying to fix right now.

Anyhow, I rechecked continuity on the GRN wire and found it was OK. My first check I think I forgot to unplug one of the brake lights, so of course it was connecting to ground.

So where I'm at now: Have power at WHT/BLK into BLFS. GRN wire has no breaks/shorts that I can detect. However, CANNOT get power from WHT/BLK into GRN wire - even a straight jump isn't working. Any help or other ideas would be greatly appreciated. I'm more confused now than I have been thus far!

tech8

Depending on how you're doing the test, you shouldn't need to unplug one of the brake lights while checking the grn wire for continuity to ground.

- If there was continuity to body ground on the green wire with it plugged in, that would indicate a short to ground on the green wire.
- If there was no continuity on the grn wire to body ground with that brake light unplugged, that may be the source where there is a short.

accordfixit

Ok, I'm not sure I understand you correctly.

With brake lights plugged in (Left/Right rear/trunk lid), there IS continuity between GRN wire and body ground point.

With brake lights unplugged (Left/Right rear/trunk lid), there IS NOT continuity between GRN wire and body ground point.

Does this mean I do in fact have a short on the GRN wire?

tech8

Yes, you may in fact have a short in the grn wire, if you are getting continuity to ground on the grn wire. The short may be in the wiring or connector(s) for the inner brake light(s).

1. Unplug the connector to the left inner brake light, step on the brake pedal, does the other brake lights come on? You can also check for power (+) on the grn wire with the voltmeter/multimeter if someone steps on the brake pedal.

2. Next unplug the connector to the right inner brake light to test whether the other brake lights work.

3. As I mentioned in one of my previous posts, you can test for continuity between the grn wire to ground on both male and female side of the connectors.

accordfixit

OK. I fixed this issue, albeit, not to factory specs. I simply cannot mess with it anymore.

Basically, I verified that the green wire was good to each brake light. For whatever reason, I cannot get current from the WHT/BLK wire to the GRN wire. It simply will not work. So I tied the green wire before the BLFS directly to the High Mount Brake light power source (Also WHT/BLK)

I've semi-permanently wired it this way, however I left everything intact enough that I could reverse this at anytime. Everything works fine, exactly as it's supposed to now. The real cause of this problem is still unknown to me, but consulting an electrical engineer, I decided that this solution was the best.

Thank you for you help and advice. Anyhow, I consider this issue fixed now!