D12 losing power for a split second

You need to check the pair of small wires for the ecm that connect to the battery terminals for tightness. If they are loose you will lost engine power for a moment whenever you hit a bump on the road. I have a 05 and also used to have a 98 that would skip with the loose wires.

 

To get help you may need a better description than just 'losing power'.
What happens with the RPM? Does it drops? By how much? How long?
I suggest an instrumented loaded test with a PTT attached that will scan and catch it when it happens.
I don't recommend a Volvo dealer unless you have no other option.
The better service you can get from a private shop that works on Volvos like yours.
Call them, give them your truck VIN, book a test and
when it's fixed come back here and update the thread.
As a courtesy and to help other owners with the same issue.

 

My problem was the air filter. My empty trailer lot is a dirt parking lot. I have to wait for the dust to settle just to back up. RPMs would randomly drop and a smoke ring would come out of the stack.