Where would you start if you fixed it? 2003 XC70 Wiring From Previous Owner, Epic Fault Codes

[daninater]

I just acquired a XC70 with disclosures that the instrument cluster wasn't working, the window regulator wasn't in good order, that there was a battery cut off switch installed--I assumed due to a parasitic drain somewhere, water pump and timing belt would need to be serviced. I've done those jobs before on my S60s, it didn't deter me. So he came down a long ways from his asking price to $2500. No rust, good interior and transmission installed by a shop with the updated servo. Clean title. It drove home a few miles and ran nicely, smooth shifts. How fast was I going? Don't know, no instruments. Radio worked too. Good heater...

That being said, I'm amazed it starts at all after looking at it more and more.

The switch is a toggle on the CEM not at the base of the battery, and I'm getting an absolute raging party of fault codes. How much of this is going to be caused from this wiring rig? I am able to get ETC and RPMs off of the OBII sensor, see a check engine light blink when I start the car.

Radiator fan doesn't engage, dash cluster still dead after I reflowed the solder on the board ( I know now because alarm). The alarm module is next on my bucket list along with how to approach this. Then the battery bypass.

I'm guessing the alarm module failed at some point and this was a work around for the previous owner or two ago to keep it rolling before all the faults. I'm not actively driving this vehicle with the fan issue on top of all the other stuff, here's some of the list, but should I start by replacing the alarm unit and then de-wiring this work around with a toggle switch?


UEM-0005 Sun Roof. Communication Fault

UEM-0004 Siren. Communication Fault

DTC SRS-00D5 SRS Indicator Lamp. Signal Missing

DTC DIM-E003 Software Fault. Faulty Communication

DTC CEM-1A5C Communication With The Upper Electronic Module (UEM). Signal Missing

CEM-1A59 Communication With The Audio Module (AUM). Signal Missing

DTC CEM-1A52 Communication With The Driver Door Module (DDM). Signal Missing

DTC CEM-1A51 Communication With The Supplemental Restraint System Module (SRS). Signal Missing

DTC CEM-1A56 Communication With The Driver Information Module (DIM). Signal Missing

CEM-1A53 - Communication With The Passenger Door Module (PDM) [CONFIRMED THIS IS UNPLUGGED to prevent window regulator from breaking]

Also, the driver seat doesn't move forward or backward. No heated seats. I only mention electrical issues if it's relevant to the computer issues I'm about to tackle. Holy moly...

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[daninater]

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[jonesg]

I unplugged my alarm module, its not worth the $250 to replace, I tried a salvage module, same problem so forget it.

I'd get rid of that toggle switch, maybe have xemodex test the cem.

Track down the parasitic draw the old fashioned way by pulling fuses.
some harnesses under the seats might have been disconnected in search of the parasitic draw and not connected again.

[daninater]

Thanks, I'll check for the seat connection I didn't think to do that. ...and get out my multimeter. I was hoping it's not grounded out well and that's causes at least some of these communication faults with various units.

[jonesg]

I'd say the fix the owner employed was worse than the problem. It caused a cascade of further problems.
So at the core of the problem you might just find a simple mistake.

[daninater]

I learned a bit more after spending a couple hours on the car.

1.) That toggle switch is hooked up to a large relay to on/off the battery in the back of the car. That relay alone is probably messing with my voltage and needs to be uninstalled, which I have a code for high/low voltage DEM-0003. Needs to come off asap. I want the alarm module and a radiator fan control on site first, it's in the mail.

2.) A contactless cable tracker confirmed there was current going through the alarm circuit with the car off, though no audible alarm. And there's an associated code with that I can read too. I'm going to pull off the alarm module and replace the battery with a 7.2V battery pack from Amazon and clean/solder the alarm module. I'm going to place the replacement battery on the outside of the repaired box so when it leaks next time it doesn't ruin the board. If my alarm box project fails I'm robbing a part from one of my other cars, 04 S60. https://www.amazon.com/dp/B07Q2H4X1J?ps ... ct_details.

3. The Bosch fan control module on the radiator housing failed and did not default with the fan running on. I know purple the signal wire needs to power it. The high speed and low speed capacitors were burned out after inspecting the unit, and there was oil damage to the controller where the wires entered that probably started it. If I had electrical components to try and fix it I would, no time, I bought a replacement off ebay for 80 dollars, confirmed fan does run. I degreased the thing with a citrus base product. I'm in North Dakota and it's cold here, I can monitor my temp using OBII and the two times I've driven the vehicle a few miles to a family garage for repair I've made sure it's been staying within normal parameters.

4. The car's dash cluster has LED lights soldered into it where the light bulbs used to be on probably six places on the board. And the gauges are blue and look after market - could be wrong about the ice blue gauges, but I thought they were green from Volvo. There's absolutely no functionality coming from the dash cluster except for a check engine light blinking when I start the car. I resoldered the voltage regulator and the pins on the ribbon cable with what I have, but I didn't go too deep into the chips yet. I need a better tool and magnification for my bench to do a better job. I'm going to revert to standard lights in case that's tripping it up. But as of now zero power, I'm holding off until the other things are finished.


When parts come in I'm going to use isopropyl to clean up the CEM, I haven't had the courage to look at that yet. I'll feel better with the alarm and fan functioning.

[jonesg]

maybe you can get a used cluster, mileage isn't stored on the odometer like the older cars, its in the ECM.
I don't know what possess anyone to bother with those vanity projects, I'm just happy when my car starts and gets me home.

[volvolugnut]

Some people should not be sold soldering irons.

volvolugnut

[daninater]

maybe you can get a used cluster, mileage isn't stored on the odometer like the older cars, its in the ECM.
I don't know what possess anyone to bother with those vanity projects, I'm just happy when my car starts and gets me home.

Right? I don't need stupid ice blue gauges or LED backlights at the cost of toasting the whole dash cluster. I want to be able to program my own. I'll take lots of picture as I un f-- I mean, un-tangle this mess. I'm sure there's plenty more surprises coming my way. Some of this stuff I'm more happy to mess with now when it's 4 degrees outside then in the summer.

[daninater]

maybe you can get a used cluster, mileage isn't stored on the odometer like the older cars, its in the ECM.
I don't know what possess anyone to bother with those vanity projects, I'm just happy when my car starts and gets me home.

Right? I don't need stupid ice blue gauges or LED backlights at the cost of toasting the whole dash cluster. I want to be able to program my own. I'll take lots of picture as I un f-- I mean, un-tangle this mess. I'm sure there's plenty more surprises coming my way. Some of this stuff I'm more happy to mess with now when it's 4 degrees outside then in the summer.

Lastly - Yeah, I think its around 150 for a replacement or a rebuild cluster. That's fine. I want to try and see if it's the CEM not powering it on, the replacement needs to be programmed to the car. Trying to say earlier I don't mind messing with reflowing solder joints if it's already broke though.