V70 2008 DDM (Driver Door Module) adventure

[Voldebag]

I purchased a V70 08 2.0F Manual a month ago with 145.000km for 3200 EUR. Car is in great shape, no rust, engine recently overhauled, but it went cheap for a reason. All of the small issues have been rectified now, but one has kept me stumped for the past week.

The DDM spits out errors regarding LIN bus messages, then losing connection with CEM and losing the initialization of the windows. The module is rebooting. The control panel on the driver door flashes every 2 seconds, the mirror adjustment is difficult to use and the power windows are jerky. This is also the case on the rear left door.

In addition, the car sits at 600mA current usage 24/7 due to this computer never going to sleep.

When I pull the fuse for either front left or rear left doors, the current goes down to 3mA after 20-30 minutes. I have pulled the seat, pillar covers, removed the front door and inspected / tested wiring thoroughly in both doors, all wiring 100% good.

When pulling the fuse on the rear left door module, or disconnecting the rear door or module manually, then the front control panel goes back to normal and the flashing stops, window rolls normally, initialization works again. This tells me there is some kind of conflict happening between the front and rear modules. As soon as I reconnect the rear module, the system crashes again.

Now I have come to the conclusion that the DDM (front) module is the wrong one installed. Someone has replaced it with the wrong unit, which is unable to communicate with the stock unit in the back, thus causing a crash.

This would be a very long post if I wrote up all the troubleshooting steps, but I have tried swapping the rear left and rear right modules and confirmed they are good.

So I created a diagram (see bottom) of the currently installed modules on the car. On the DDM (front left) notice how the date and numbers don't match up.

I would like to replace the module with the same as original, but there are so many of them online that I simply am unable to find the one that should fit my car. I have spoken with my dealership and they are only able to come up with a volvo part number, (31295207) which is not visible anywhere on these modules.

My closest guess is these two, but they don't have the exact same number, but they seem to be the exact same module with a few months between them in production.

7G9T 14B533 ED
05 0791 42 00
https://www.totalparts.nl/eng/car-pa...4t14+2009-2010

7G9T 14B533 EC
05 0791 41 02
https://matchapart.com/partpage/volv...24-091736053/0


Now to my question: what module should be installed?

Any insight would be appreciated, or if another owner of this vehicle could confirm what module they have installed and compare to the other 3 modules installed in their car versus the diagram below. I am going to purchase one of these modules above and when I get back from vacation next month I will post an update. I am leaning towards the first module as it carries the same "SW" tag ending (AD) as my other 3 modules.





One more thing that led me to the DDM being weird is the voltage reported by the X/Y Axis DDM-Driver rear view mirror. Reporting as 17.98V compared to the other side reporting 11.9-12.0V.

[FreshAir]

Top fault finding! Can't help you with the part number though.

Good luck with final fix.

[Voldebag]

Only a few minutes after ordering the module from ebay did I realize that perhaps the issue is software related, the module might need a simple reload.

I was quoted 200 EUR from my local mechanic for a DDM reload in 6 weeks. I will wait for my new module to arrive and hopefully the software that is already configured on it is compatible with my car. It only cost me 40 EUR with shipping to purchase the module so no big loss there.

The module I ended up picking:
7G9T 14B533 ED
05 0791 42 00

HW: 14C235 EA
SW: 14C064 AD
Dat. xx.03.08

[Tatsfield]

A cheap VIDA/DiCE clone would help you in this sort of situation and would be there for the future puzzles that an old Volvo can set for you.