Solved! 04 V70; Brake lights don’t work, position lights stay on with ignition off Topic is solved

[- Pete -]

Skip to the last post to view the resolution to this issue.


I rarely post on the various Volvo groups, but I have an issue that has me stumped. I’m beginning to feel like I’m missing something obvious & simple. I have roughly 400,000 miles of experience with P2’s specifically & haven’t encountered an issue where the solution was as elusive as is the one to this problem.

This one has to do with brake lights. I crashed the car in question a year ago, banged up the drivers side; specifically the front corner, drivers door, and rear corner. Headlight & taillight housings were smashed.

I’ve fixed the damage & am now troubleshooting why my brake lights don’t work. Here’s what works, what doesn’t, and various oddities.

Known:

Brake lights (aka position light) sort of don’t work…
Fuse 4 (backup lights) in REM was blown due to shattered tail lamp housing & shorted contacts
Fuse numbers 30 & 31 (parking lights) in L. dashboard wereblown
Burnt REM shunt (see photo)
Brake lights/Position lights come on and stay on 15 seconds after (& with) ignition off
3rd brake light flickers with ignition off, shuts off if you open the hatch
Brake lights come on if I pull relay RMA1 (2/52, 15i feed, rear)

3rd brake light works but only with ignition OFF & only after 15 seconds after switching ignition off. 3rd brake light doesn’t work with ignition on, but begins to work only after 15 seconds after switching ignition off.

Things I’ve done/things that work:

Swapped brake pedal switch from different car - no change
Swapped REM with same model year car - no change. In fact, the REM out of the car in question worked perfectly in the other car I swapped it into. The REM swapped into the car this post is anout made no change at all.
Headlights (high/low) & fog lights work
Rear fog lamp works
Reverse lights work
Parking/running lights front & rear now work
Turn signals work
Rear wiper works
Rear cargo area light works

Any ideas? I checked all the fuses in all the (3) locations (I haven’t pulled the CEM yet though). I replaced a few blown fuses (all blown fuses were due to the headlight & tail light housings being smashed & shorted contacts), i replaced the burnt shunt I’d found in the REM. ViDA scan done & can post what I found there. CEM-1A5A seems probable. While I can fumble around in it & eventually find what I’m after, ViDA use is certainly not my strong suit!

Thank you.

- Pete -

[DavidE7]

As you are aware after wrenching on several Volvos for a long time, cars produced for worldwide consumption get weird features. In Germany there is a requirement for a left rear fog lamp. The bright light that is on in your picture is the rear fog lamp (I had to check on my XC70 to verify it is that particular bulb). There is a button on the bottom row of the headlight module for turning it on and off.

I lived in Germany for a few months and I would see cars parked on the street with their ass sticking out a bit and that light was left on. There is a trick on some EU cars for being able to turn the car off and having that bulb stay on so the rear corner of the car doesn't get hit. Try unplugging the headlight module and see if the light stays illuminated.

[- Pete -]

As you are aware after wrenching on several Volvos for a long time…. The bright light that is on in your picture is the rear fog lamp (I had to check on my XC70 to verify it is that particular bulb). There is a button on the bottom row of the headlight module for turning it on and off.

Yes sir, of this I am aware. It wasn’t the photo I had wanted to share - I thought I had a photo of the car with just the position lights illuminated & ignition off. My wits are becoming fragile evidently.

The rear fog light functions as it should. The position/brake lights are the only ones I haven’t successfully been able to troubleshoot. Some of the other groups I posted this in are suggesting the wiring is the most likely culprit since I’ve comprehensively evaluated component integrity (fuses, REM, relays, shunts, bulbs…)

[Vova585]

With Vida erase all the codes. Try to do 2-3 start/stop cycles without pressing the brake pedal. Recheck of you have any codes. If no codes I would interpret it as a good sign(self test is good). If code is immimediatly present(hard code, system self diagnostic recognizes issue on start cycle) I would check power and ground to the REM with load light of 2amp. If those check good and we know the rem from the car works great in the test car- issue is likely in Can twisted wire pair. Maybe some body metal pinched it, or not careful body work cut,repair.

[DavidE7]

I try to save the original list of codes for reference before erasing so I know if the code is a repeat. That is a long code list! There is a tab where you can print the codes and I select print to PDF to save them.

I had problems with the CEM module and the right turn signal not flashing and not turning off. It turned out to be a fried TOPFET on the CEM PCB. There are also TOPFETs in the REM for controlling lights. Search for TOPFET. The TOPFETs can be replaced for much less money than sending in the REM for replacement with software transfer.

Good luck!

[- Pete -]

I try to save the original list of codes for reference before erasing so I know if the code is a repeat. That is a long code list! There is a tab where you can print the codes and I select print to PDF to save them.

I had problems with the CEM module and the right turn signal not flashing and not turning off. It turned out to be a fried TOPFET on the CEM PCB. There are also TOPFETs in the REM for controlling lights. Search for TOPFET. The TOPFETs can be replaced for much less money than sending in the REM for replacement with software transfer.

Good luck!

I have been arguing with this cars post-accident gremlins for well over a year now so I apologize if it seems like I’m frustrated & that I can’t keep my sh!t straight anymore. Now I am second guessing my steps when I test-swapped in the known good REM yesterday... I’ve done & repeated so many tests & spent so many hours on ViDA I’m beginning to forget what material I’ve already digested…what ground I’ve already covered. Specifically, now I am wondering if I even remembered to put the brake light bulbs back into the tail light housings when I tested the known good REM. You see since the brake lights/position lights come on by themselves with the ignition OFF, if I leave them installed, the battery will be sapped in no time. In fact, even with them removed, the battery (which is a brand new group 49 (the largest that will fit)) will be sucked dry in a short amount of time (days) since there is this parasitic draw happening (3rd brake light flickering with ignition off).

[- Pete -]

With Vida erase all the codes. Try to do 2-3 start/stop cycles without pressing the brake pedal. Recheck of you have any codes. If no codes I would interpret it as a good sign(self test is good). If code is immimediatly present(hard code, system self diagnostic recognizes issue on start cycle) I would check power and ground to the REM with load light of 2amp. If those check good and we know the rem from the car works great in the test car- issue is likely in Can twisted wire pair. Maybe some body metal pinched it, or not careful body work cut,repair.

Apologies for not responding sooner. Here is what I show on ViDA this evening. I don’t recall seeing the REM-1A05 code before. When I look that up it tells me the supply voltage relay (RMA1 in REM, 2/52, 15i rear feed) has signal missing or signal low, check for short circuit…

I have yet to find a wire or connection that makes me cringe. Of course, in the headlight & tail light housings that were smashed there were mangled contacts. Yet the car-side wiring (and connectors!) all appears to be unharmed.

So thinking that this relay might be fried I pulled it & the brake lights come on immediately after removing it. Obviously this is without pushing the brake pedal. I swapped it with a known hood relay & no change in behavior.

IMG_1843.jpeg (171.37 KiB) Viewed 762 times

[abscate]

I’ve got a carcasses 2004 in Albany of you need any parts. Whew, that’s a nasty one

[Vova585]

I feel sorry for you on this one. Pass of least resistance if money is not a prohibiting factor- send Rem to xemodex and let them verify it is all ok. If such is not an option, try to locate wiring diagram to the REM. Let's focus on that relay and see where it brings 12v. Knowing which fuse it feeds from(for example 5amp) we can substitute load with 55w bulb and see if it is able to make ot shine bright, if not- maybe fuse contact or fuse itself are faulty. If nothing like that would be discovered, I would try to cut the wire and supply 12v through the fuse to the power side and see if anything will change. Another wild option if DavidE7 can look at your REM and see if he can fix it for a fee(much respect to him for being able to fix his unit with all involved soldering)

[- Pete -]

I feel sorry for you on this one. Pass of least resistance if money is not a prohibiting factor- send Rem to xemodex and let them verify it is all ok. If such is not an option, try to locate wiring diagram to the REM. Let's focus on that relay and see where it brings 12v. Knowing which fuse it feeds from(for example 5amp) we can substitute load with 55w bulb and see if it is able to make ot shine bright, if not- maybe fuse contact or fuse itself are faulty. If nothing like that would be discovered, I would try to cut the wire and supply 12v through the fuse to the power side and see if anything will change. Another wild option if DavidE7 can look at your REM and see if he can fix it for a fee(much respect to him for being able to fix his unit with all involved soldering)

You know, after swapping the REM’s between 2 of my like year P2’s and seeing no change (in either car), I am less than convinced the REM is to blame. That being said, I know for a fact that my P2 knowledge is far from limitless and can conclude that I am also less than convinced that I am correct in my assertion just prior to this sentence. One thing is for sure - something is afoot, amiss … awry ...

I came across this this evening in ViDA. Seems like a good place for me to spend some time. I will post my findings. Thank you for putting up with me.