2001 XC70 UEM, Sunroof, Alarm, Alarm Siren repeated attempts

Sailsman · Post by **Sailsman** » 07 Jun 2023, 16:55

Hi All, So the battle continues...trying to get sunroof to close and dome lights to stop cycling on and off while driving (no door open/tailgate open codes as far as the lights go)

Removed alarm siren, cut open, replaced siren battery, circuit board looked good and old battery hadn't leaked. Sealed up the siren. I waited half hour after turning off the car before disconnecting neg. at battery and replaced it in the wheel well. I returned fuses 28 and 38 back into the fuse panel. Re-connected Negative cable with key in pos 2. Lock/unlock 3 times.

Sunroof still does not work and if I lock the car with window down, the alarm light on dash flashes, but if I reach in and open the door, the head/taillights flash but no alarm sounds.

I have also tried just pulling fuse 38 alarm siren and trying the sunroof. no luck.

I have no codes on the left side information screen about alarm module service or any other codes there.

If I press the left stalk and the foglights twice the information screen checks all the modules and it says UEM not checked.

I have repeatedly tried the lock/unlock 3x

Finally, I opened up the dome lights to drill out the rivets on the sunroof gear to manually close it according to a previous post here, but apparently on the 2001 xc70, you can only reach 2 of the rivets, the other 2 are further back behind the fabric head liner and inaccessible.

I'm down to
1. UEM is bad (but wouldn't I get a code for that) or
2. previous owner replaced rear view mirror/uem and never had it re-coded (but then the alarm should not work at all correct? (I have flashing lights/no siren).
3. Alarm siren still bad despite new battery (but shouldn't pulling fuse 38 then solve it)?
4. I shouldn't own volvo's.

Thoughts?

Post by **firstv70volvo** » 08 Jun 2023, 08:25

Sailsman wrote: ↑07 Jun 2023, 16:55 Hi All, So the battle continues...trying to get sunroof to close and dome lights to stop cycling on and off while driving (no door open/tailgate open codes as far as the lights go)

Removed alarm siren, cut open, replaced siren battery, circuit board looked good and old battery hadn't leaked. Sealed up the siren. I waited half hour after turning off the car before disconnecting neg. at battery and replaced it in the wheel well. I returned fuses 28 and 38 back into the fuse panel. Re-connected Negative cable with key in pos 2. Lock/unlock 3 times.

Sunroof still does not work and if I lock the car with window down, the alarm light on dash flashes, but if I reach in and open the door, the head/taillights flash but no alarm sounds.

I have also tried just pulling fuse 38 alarm siren and trying the sunroof. no luck.

I have no codes on the left side information screen about alarm module service or any other codes there.

If I press the left stalk and the foglights twice the information screen checks all the modules and it says UEM not checked.

I have repeatedly tried the lock/unlock 3x

Finally, I opened up the dome lights to drill out the rivets on the sunroof gear to manually close it according to a previous post here, but apparently on the 2001 xc70, you can only reach 2 of the rivets, the other 2 are further back behind the fabric head liner and inaccessible.

I'm down to
1. UEM is bad (but wouldn't I get a code for that) or
2. previous owner replaced rear view mirror/uem and never had it re-coded (but then the alarm should not work at all correct? (I have flashing lights/no siren).
3. Alarm siren still bad despite new battery (but shouldn't pulling fuse 38 then solve it)?
4. I shouldn't own volvo's.

Thoughts?

Have you tried unplugging the siren control module and then seeing if the sunroof works? There is a single serial data line from the UEM that is shared with the sunroof and siren and if the siren is pulling this line down the sunroof won't work and why to disconnect to see if this is the problem.
Do other UEM functions appear to be working; garage door opener, seatbelt reminder, any problems with the climate control module?
Is the sunroof fuse okay, fuse 34?
When did the sunroof stop working, anything else not working at the same time?
When the dome light comes on while driving do you hear a chime at the same time, does it go out quickly?

Post by **vtl** » 08 Jun 2023, 12:03

Sailsman wrote: ↑07 Jun 2023, 16:55
3. Alarm siren still bad despite new battery (but shouldn't pulling fuse 38 then solve it)?
4. I shouldn't own volvo's.

Thoughts?

As firstv70volvo said. Siren and sunroof share the same LIN-bus. Siren is known to go bad over time and cause LIN communication problems, resulting in nonoperational sunroof.

I fixed my siren a few years ago. Now it seems it is bad again, draining my main battery. When I have time, I'll pull it out and rework to battery-less setup or throw out completely. May finally use my CEM pin cracker to get the pin and kick the siren out of CEM configuration. I don't even lock my vehicles, why the siren is even there?

Sailsman · Post by **Sailsman** » 10 Jun 2023, 07:20

Thanks for the replies.
I will be disconnecting the siren when I am under there replacing the cv axle. Even though I replaced the battery in it and the circuit board looked good, the siren still did not go off, but the headlights, etc. do flash when the alarm is triggered. I don't care about the alarm anyway except for it's connection to the sunroof.

The sunroof module fuse 34 is good

Seatbelt reminder works, Unknown if garage door buttons work, Climate control works fine.

As for the dome lights, they start to turn off as normal and then light back up. This cycle just keeps repeating, they start to cycle off, then cycle on over and over again. There are no codes for open door, tailgate, etc.

Frustrating to say the least.

Post by **jonesg** » 10 Jun 2023, 08:45

I unplugged my siren 3 yra ago, sunroof still works, but I never use it .
Not sure if I unplugged the siren or just removed the battery. Either way, I still get one without the other.

93SCMax · Post by **93SCMax** » 10 Jun 2023, 11:42

If your siren isn't working, wouldn't that indicate that you put a good battery in a bad siren?

I know it's expensive, but I replaced my siren a few years back and have not had a problem since. It had a dead battery.

Volvo electricals are complicated. When something isn't connected properly or at the right voltage, bad things happen. Think about getting a new siren.

Post by **vtl** » 10 Jun 2023, 12:13

93SCMax wrote: ↑10 Jun 2023, 11:42 Volvo electricals are complicated. When something isn't connected properly or at the right voltage, bad things happen. Think about getting a new siren.

That applies to all cars. Anecdotally my Tundra was having a brake system failure when I depressed the brake pedal. It turned out to be an aftermarket LEER cap that draw power from the stop lamps and somehow that upset Toyota. Solved with a small battery for dome lights, its own charge controller and a diode.

Sailsman · Post by **Sailsman** » 12 Jun 2023, 02:26

93SCMax wrote: ↑10 Jun 2023, 11:42 If your siren isn't working, wouldn't that indicate that you put a good battery in a bad siren?

I know it's expensive, but I replaced my siren a few years back and have not had a problem since. It had a dead battery.

Volvo electricals are complicated. When something isn't connected properly or at the right voltage, bad things happen. Think about getting a new siren.

Thanks, Yes I'd say that is certainly the case. Though the board looked good, it was obviously just a visual. I really don't care about the siren except its effect on the sunroof (mine is partially open) so I'm not going to buy a new siren due to its price. I'll unplug it when I'm under there replacing the cv axle and do all the resets, etc. and see how it goes. I wanted to post anyway to make sure there was not some other item i was missing.