As the title says, my brake lights are out, and the console is throwing the "Check brake light" error.

Bulbs have been replaced, mechanic said they were good, and old ones were definitely blown. Fuses are good -- replaced them anyway, still no go.

The brake light at the top center of the glass works great, just the lower taillights.

Any ideas of what to specifically look for? The mechanic is not Volvo-specific or trained, so he will not be working on the car.

Thanks!

 

You have replaced both the bulbs and the fuses? If it is still a "no go" I would have to assume that there may be something wrong with the wiring at this point. Bad ground perhaps? Maybe "tech" or someone else can shed a little more light on this subject.

 

Yes, both bulbs have been replaced with the appropriate OEMs, and the fuse looks fine (#3 in the trunk, 15 amp) but I replaced it anyway.

I'm hoping that this is something semi-common -- wires and harnesses/clips look fine as well -- nothing loose, crimped, or bare. I haven't had any other electrical issues with the car, and I've owned it for about 6 months.

Thanks again --

 

Does your Mechanic have a Scanner that can Read all the systems in the car?

 

No, unfortunately this one doesn't. The dealership wil, but with the volume of the dealership in Austin -- it'll be a full day before they can take a look once I drop it off, and of course, there's probably a large service cost.

So yes, I am choosing to evade the direct fix (dealership) method right now, in hopes it can be fixed or diagnosed otherwise.

 

It is very hard to Fault trace them without the Computer hooked up.

That is because the Fuse Box in the trunk is actually a computer. The computer tells the lights to come on.

They are known to Mess up from time to time.

Is there anything else not working in the car? (Anything All info little or big will help)

Has anyone changed the Battery lately?

 

In reverse order:

Yes, I changed the battery 3 months ago with no issues. It was a volvo-approved replacement with no complications.

Everything else in the car is acting normal -- I need the front control arm bearing bushings replaced (.09 part, $500 labor, yay) and the no-neutral transmission software change, otherwise a-ok.

Not to distract you with a semi-unrelated question, but if the computer in back was telling the lights not to come on, would it still give me the Check Brake Light error? I guess I wouldn't expect a system of checks and balances like that -- one part says it's ok to be "off" and another part argues "no wait, that's wrong!".

 

The reason I asked because if one computer has a fault it can mess others up.
They are all on a Network.

Make sure no wires at the Battery Terminal broke off.

 

There are 3 wires on the battery, negative, positive, and a black wire on another screw on the positive connection. If I recall correctly, this goes to the computer/fuse box in the back.

If this is a computer issue, would disconnecting the battery neg, and resetting the ECU help? Maybe indirectly or temporarily?


Also, are there any wire harnesses or clips that connect both brake light terminals? There are three on the left side of the car and two on the right -- none seem interconnected. Bulbs or fuses bad, or a loose wire -- that's my fault. I'm trying to identify things I may have broken.

 

Not that I am aware of on the wires being connected.

Maybe the Battery disconnect might Help. Disconnect both terminals and hold them together for 5 minutes then connect.

After doing that make sure you also lock and unlock the car to wake the car up.

 

Disconnect and then hold them together? That's strange. Didn't know about the wake up either.

To add some more confusion, I backed into a spot at work today and the rear of the car was reflected on the glass -- brake lights came on twice (two taps), then not again. I wasn't moving, nothing changed between working and not working -- doesn't sound like a loose wire to me b/c of that.

 

Maybe on the the Relays for the Brake lights in the Rear fuse panel.

Yes when you hold the cables together it discharges the Capasitors.

 

Where are the relays and what do they look like? I thought they'd be up front, so I hadn't even checked them yet. That was one of my original concerns along with bulb/fuse.

Thanks again Tech.

 

You should see then easy if you fold the Panel down on that side.
Black square relays or long skinny things called shunts.

 

Well, that's a no-fix on the battery solution. Oh well.

Kind of a similar question, what is the black box w/ red wires right beside the main battery in the trunk? I thought maybe something there may have been jarred (although it looks ok).

I'll go out and check those relays now.

 

Sorry to double-reply -- Tech -- is the error I'm getting the one the car would throw if they were the wrong bulbs? VatoZone computer says those are the ones I need, comparable to the P21W -- originals and replacements are both Osram, however originals say 50065 and the replacements says 5006 or something similar -- the packages are still in my trunk so I can't look at the moment.

Nevermind just checked, original is OSRAM7506L, replacement is OSRAM7506LL, the long-life version. Both 12v P21W.

 

Check out link and see if you can find which is the Brake relay and swap it with another and see if it changes.
http://www.volvotechinfo.com/WD123/

 

Thanks again tech, great resources there.

Unfortunately, I don't have anything plugged into the spots meant to be brake lights. I was going to trade brake lights and rear fog light.

The schematic shows every relay slot filled, whereas mine is missing about the top left 1/4 to 1/2. No, those relays aren't in a pile underneath the box, either

 

Yes the wiring Diagrams give every option possible.
Also if you want you can also check and swap with one under the hood.
There is many relays in the car.

 

I guess I'm confused -- there is no relay plugged into the spot for "brake light" or even "tail light, backup light".

Just the slot. Does it matter?