Brake light failure 2008 S60

evm1024 · Post by **evm1024** » 21 Jul 2025, 22:06

We have a 2008 S60 2.5T FWD sedan that does not have brake lights. The 3rd light does light and we also get the stop light message on the dash readout when braking.

I have access to a S60 electrical diagrams Manual for a 2007 (TP 3997202) and hopefully that is compatible with the 2008.

There are some odd goings on in that at times pressing the brake pedal will turn on the stop lamps at least for a little bit of time.

I've removed the REM, opened it up and made sure there was no obvious issues with it. There was a few small spots of corrosion on the ribbon cable that I cleaned up with deoxit5 and a tooth brush. All the fuses were removed and checked as well as had their contacts cleaned.

I have not checked the relay yet. I just don't know which one is in the brake circuit. See the photo and let me know which one.

I'm guessing that the switch 3/9 is the actual brake light switch. This feeds into the CEM on C:34 then heads to the REM via CEM-A:15 to REM A-18. The diagram (page 62) indicates that the stop light voltage exits on REM-B:3 and to the lamps. I'm also going to have to guess that there is more to it than that.

The only code that we get is CEM8D01.

There is another thread (viewtopic.php?t=89887) But that 2007 has a different REM than my 2008. Back to the question - Which relay?

Thanks!

Post by **abscate** » 22 Jul 2025, 05:59

I have an ongoing issue with my 2005 REM FUSES that develop a coating every 2 years or so. The fuses test good, but I have to scrape the metal to get my lights to work.

No codes or light warnings on dash.

Bot h brake and tail lights have been affected

See here

viewtopic.php?f=9&t=73056

evm1024 · Post by **evm1024** » 22 Jul 2025, 21:41

Fuses are good and have been cleaned. I'm working up the chain that's why I will check the relay next. I might have to draw out some of the connections onthe PCB and see if it is up stream.

evm1024 · Post by **evm1024** » 28 Jul 2025, 19:23

Continued to work on this issue. The code I get is: CEM8D01. I've gone through the REM and even traced some of the circuitry. One thing that was confusing me is that the 3rd brake light comes on but not the main brake lights. Except the main lights will briefly flash when first pressing on the brake pedal on initial start up. Then they will not light. Mostly... Once in a while they will work a few times.

One thing that has thrown me is that the 3rd brake light appears to use a different switch that the main brake lights. A redundant system it appears. I tested this by removing F5 of the CEM (main brake switch fuse) and the 3rd brake light operated correctly.

I will see about cleaning the contacts on the CEM connectors and see if that helps. The step after that would be to remove the CEM and see if there is any internal corrosion. Looks like a bear of a job to remove it and a big job to replace it at least in terms of cloning the VIN and such.

Post by **MoVolvos** » 28 Jul 2025, 19:30

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On my 2002 V70 XC it was the bulb socket metal contact strip on the brake assembly itself which had come loose from the plastic. Would loose the bulb from time to time so took a few bulb swaps and checking of wiring and sockets before I saw the strip had come loose from the plastic.
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: Volvo Rear Brake Light Assembly.png (631.08 KiB) Viewed 247 times

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evm1024 · Post by **evm1024** » 28 Jul 2025, 19:54

Thanks for the reply.

I was worried that it might be a grounding problem so I tested for that. With the brake connector removed from the REM I was able to apply 12 volts to pin B3 which feeds the brake lights. Both brake light lit up. There are individual grounds for the left and right brake lights so a bad ground would only effect one brake light.

Page 62 in the manual I'm using shows that fuse F5 on CEM feeds 12 volts tot he brake switch 3/9 which returns the signal to CEM/C:34. What happens in the CEM at that point I don't know. In any case CEM/A:15 is the brake light signal that leaves the CEM and goes to REM/A:18. The schematic shows that A:18 goes into the REM and then directly out again via B:3 which feeds voltage to the brake lights.

I'll wiggle a few connectors and if that does not help then I might as well follow the signal from the brake switch all the way to the brake lights so as to see where is fails. Right now it looks like the only 2 choices are the brake switch or the CEM.

Post by **jonesg** » 29 Jul 2025, 06:33

How can it be the brake switch if the center brake light works.

evm1024 · Post by **evm1024** » 31 Jul 2025, 19:12

jonesg wrote: ↑29 Jul 2025, 06:33 How can it be the brake switch if the center brake light works.

That is part of what makes understanding this error so puzzling. It turns out that the switch at the foot pedal activates the main brake lights. There is another switch on the vacuum assist in the engine compartment that activates the 3rd brake light.

I got some more insight as to the problem from this forum post from Sweden: https://www.jagrullar.se/forum/viewtopic.php?t=73376

The brake lights are now working. See next post.

evm1024 · Post by **evm1024** » 31 Jul 2025, 19:33

Well I did not find a smoking gun but all my prodding has solved the problem. To recap:

Both main brake lights failed to light. When braking a brake light failure message displayed. The 3rd brake light works. A CEM8D01 code was read.

My car is a 2008 S60 with a newer version of the REM module. Earlier versions had a set of relays. In my car no relays and the brake light voltage enters REM/A:18 and exits REM/B:3. Just a jumper through the REM.

This indicates that the fault was not in the REM but was upstream in the CEM or the actual switch on the brake pedal. With a cloudy dat in the forecast (read that as not baking in 95* sun) I pulled the CEM out of the car. What a pain but with a quick search oy youtube I found a video of the procedure.

CEM in hand on the bench I opened it up and with visual inspection found no corrosion on the connectors but a little corrosion on a few of the PCB traces. DeOxit-5 and a toothbrush took care of that. With the CEM out I also pulled all fuses and gave them and their connectors a dose of DeOxit-5.

While I was at it I pulled the brake switch from the pedal. This was shown to be functional and self adjusting. The switch was returned to its mounting and adjusted (search youtube for an example).

With everything, connectors, fuses, PCB cleaned up it was all re-installed and tested.

If I had to guess what was the cause I would hem and haw. But this is my wife's car and having brake light is important. I'll take the win...

P.S. She would like a Jaguar - If we do get one it would be a 2000 model XK. Working on her S60 is likely good training!

Post by **DavidE7** » 01 Aug 2025, 21:37

I had a 2003 Jaguar S-type with a manual transmission at the same time as when I got the first Volvo V70 for my wife. The Lincoln LS/Jaguar S-type/Ford Thunderbird was the first vehicle I was responsible for engineering and testing a part on. Volvo and Jaguar are very different cars with limited overlap in the parts suppliers and repair procedures. I did some vehicle performance testing on the X100 (XK8) when I worked at Ford. It has excellent dynamics at high speed but is a huge car for the small interior. My S-type was severely infected with tin worm when it was rear ended and totalled. Jaguar steel is much less protected from rust compared to the P2 Volvos of the same era. Make sure you watch some YouTube videos for the rust prone areas!