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02 XC70 Alarm Siren/UEM Woes

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo's stylish, distinctive "P2" platform cars.

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BeachWagon
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02 XC70 Alarm Siren/UEM Woes

Post by BeachWagon » Mon Aug 12, 2019 12:24 pm

AS the title states, I have a 2002 V70 XC that I just picked up with a few problems. The sunroof and dome lights do not work. The information screen does not say anything about servicing the alarm system. My scanner can normally connect to the UEM in p2's such as my 02 V70.[we have a few wagons!]. The scanner was unable to connect to the XC70's UEM.

First repair attempt was disassembling the mirror, where several cold solder joints were taken care of. No change in the car's behavior. To be clear, the UEM is inside the mirror correct?

Second repair attempt was replacing the alarm siren module battery. The original battery was corroded to the point that the wire became disconnected. No damage to the PCB. Now that the alarm siren battery has been replaced, the alarm goes off for around 30 seconds, then shuts off for around 30 seconds. It continues this cycle over and over.

As a side note, the alarm siren will still go off even after i disconnect it from the car. If I unhook the siren battery, it stops. I can reconnect the siren battery and it will not go off until the siren is hooked back up to the car.

So here I am asking just what the hell is going on? I do not have Vida....working on that as one of my next purchases.



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oragex
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Re: 02 XC70 Alarm Siren/UEM Woes

Post by oragex » Mon Aug 12, 2019 1:39 pm

I think it would be normal for the module to keep sounding when it's disconnected. The correct battery is 7.2v 240mAh is if remember well - those chinese Ebay batteries have lower mAh and may not last many years

The alarm starts ringing when the something is not locked - maybe a trunk/hood/door micro switch is bad. Also check the 38 siren fuse (5amp I think). Another scenario to trigger the siren, is when the car battery is disconnected while the car is locked - maybe look at the power wires ?

The UEM is inside the rear view mirror indeed

Does the sunroof work when you unplug the siren module ? Should work. If not, try locking unlocking the driver's door 3 times with the key fob. See if it changed anything


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BeachWagon
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Re: 02 XC70 Alarm Siren/UEM Woes

Post by BeachWagon » Mon Aug 12, 2019 3:21 pm

I used a 7.2v 700mah Nimh battery. It's a replacement cordless phone battery. It does power the siren. Siren has since stopped. I suspect the battery was low on charge. Getting back to the UEM...my scanner is still unable to connect to it. CEM reports communication error with UEM as well. At this point, I believe the siren module is fine and I should be redirecting my attention to the UEM. Sunroof does not work when siren is unplugged. I've tried unlocking the door with the key three times as well as setting off the alarm and shutting it off by unlocking the door. No dice. I can't use the fob either so I know well there are still problems with the UEM. I'm a little suspicious of the voltage regulator on the UEM board. Gonna check that.



mark99tj
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Re: 02 XC70 Alarm Siren/UEM Woes

Post by mark99tj » Tue Aug 13, 2019 9:23 am

I had an issue last month where my battery was drained. I had parked my 2002 V70XC in my garage with the windows and sunroof open, and accidentally hit the panic button on the alarm (and my alarm does not sound due to the typical problems) and the lights flashed all night without me knowing and the battery drained. I had to jump the car in the morning, and once I did, the sunroof would not close. After trying a number of things, I pulled the fuse for the siren module. After putting it back in, essentially resetting it, the sunroof worked fine. From researching on other forums there does seem to be some sort of electrical interaction between the siren and the sunroof.



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RickHaleParker
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Re: 02 XC70 Alarm Siren/UEM Woes

Post by RickHaleParker » Wed Aug 14, 2019 3:28 am

mark99tj wrote:
Tue Aug 13, 2019 9:23 am
From researching on other forums there does seem to be some sort of electrical interaction between the siren and the sunroof.
They are both on the same CAN Bus. If one or the other pulls down the CAN Bus. The UEM loses communication with both.
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Platform: P80 1998 C70, B5234T3, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.

Platform: X40 (Nedcar) 2003 S40, B4204T3, AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.

Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0, Plant Torslanda Sweden.
----------------------------------------------------------------
1997 S90, B6304S, AW30-42, Bosch Motronic 4.4 - Sold

BeachWagon
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Re: 02 XC70 Alarm Siren/UEM Woes

Post by BeachWagon » Wed Aug 14, 2019 5:25 am

Yes, and if the UEM is dead[as it is in my case], it takes the keyless entry, sunroof and dome lights with it.



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Re: 02 XC70 Alarm Siren/UEM Woes

Post by RickHaleParker » Thu Aug 15, 2019 9:47 am

BeachWagon wrote:
Wed Aug 14, 2019 5:25 am
Yes, and if the UEM is dead[as it is in my case], it takes the keyless entry, sunroof and dome lights with it.
Fuse 11C/6 .... ?


Platform: P80 1998 C70, B5234T3, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.

Platform: X40 (Nedcar) 2003 S40, B4204T3, AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.

Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0, Plant Torslanda Sweden.
----------------------------------------------------------------
1997 S90, B6304S, AW30-42, Bosch Motronic 4.4 - Sold

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