Hello,

Newbie here, but not new to playing with cars. I recently tackled replacing the fuel pump on my XC90 (known leaking issue). Everything went just fine, but I'm stuck on an issue "after" I put everything back together. I had the battery disconnected, but reconnected it to be sure the pump/lines sealed and I had no leaks. Once I was all done, I put all the seats back in and here is where the problems started. I got a SRS Alert which was my fault. The center seat SRS sensor was disconnected when I reconnected the battery and tested the pump. Here comes the SRS error code. Ok I knew I'd have to get to the dealer to reset it. But the real problem is I now have a fault code of "Check Stop lights". It seems "both" left and right stop lights don't turn on but the center bar does. All other lights/functions on the entire car are perfect. I checked the fuses and none were blown, so I am suspecting its the relay in the left rear compartent. But I can't find a diagram to tell me which relay is for the brake lights. Or is it possible I may have dislodged one of the connectors under the seats when I worked on the pump? I checked those and found nothing wrong. Just got back fron Volvo and they charged me $75 to reset the SRS code, but they wanted $300 to $400 to figure out the stop light issue. They weren't kidding so I said no thanks. I mean I didn't touch any electrical connectors in that repair except what was needed for the fuel pump. Any suggestions? I even asked Volvo to provide me with the diagram for the rear compartment relays to test the stop light relay (I have a spare), but they said "Oh, we lost that page in the service book". I take that as a pay me my $300 and I'll fix it for you lie.

Oh, and both bulbs are fine and I installed new ones just to eliminate that potential issue.

Let me know. I won't drive the car without the brake lights working.

Thanks.

 

see my private message

 

I was able to secure a copy of the wiring diagram for the XC 90. I have now tried replacing all the fuses relating to the brakes, both bulbs (again), i switched the brake relay out in the rear compartment REM, I have taken out the rear seats again and doubled checked all the connections.

Nothing, zero zip. I still have the upper center bar coming on when the brakes are applied but still not the two outer lights. All other rear lights and entire electrical system in the car is functioning perfectly.

I really don't know where to go from here. I have heard that sometimes the relays need to be "woken up", but I'm not sure how to do that other that replacing it. Would having the rear compartment REM reset do anything and is that possible? Is that something I can do or do I need the dealer to hook up their computer to test all the computers?

 

Finally!!!!

After going over every electrical component and connector that I thought I could have damaged when I replaced the fuel pump, plus going through all the fuses, and relays, the last and final check I did was to completely replace the brake relay in the left rear compartment and PROBLEM SOLVED!!!

What's really strange is that's where I actually started to look for the problem. I switched another relay (exactly the same) from my fog lights, and tried it in the brake relay location and switched the brake relay over to the fog lights. The fog lights worked but the rear brakes still wouldn't function. So I switched everything back.

Why replacing the brake relay with a completely new one did the trick is another mystery.

But, the long story is, the fuel pump replacement had nothing to do with the brake lights going out as I suspected. How the lights went out coincidently at the same time as the completion of the work on the fuel pump is why I chalk it up to "its a Volvo, what do you expect".

Thanks for sticking with me on this one.

RacerX

 

I have this feeling ever since we bought the XC90 -waaayyy tooo many problems (some dealer-induced).

Anyway, congrats on fixing the brake lights!

 

Hi there,
I have the same issue with the brakes on my XC90. I couldn't get to the relay or take out the fuse panel so I can replace it.
Could you please share the steps or a video if possible on how to get to the relay or take out the panel to get access to this relay. I assume other people had similar question, but I couldn't find the answer by searching this forum.
Thanks for your help.

 

1) check fuse 14 in the driver's side rear cargo area fuse panel

2) check RM15 in the relays