Hi Judgey,
Sorry to revive this old thread but my 2004 2.5 V6 FL has similar issue that scanner read SRS DCU come back with "Internal Fault(replace SDM)", and SRS light on the dash won't distinguish following pre-ignition bulb check of 5 sec. I have also cut the under heater-assembly carpet and sourced a second hand YWC000610 DCU off the ebay. I have a few queries that need your kind confirmation before I start my attempt to diy:
2. did you remove the heater assembly or by removing the carpet there would be enough room for the swap?
3. the swap is like a direct fit without any programming involved?

Thanks a lot.