Ok, it could well have an EGR valve that has a vacuum shut off flap, which activates when the DPF is doing a regen.
The problem with a basic code reader, is it doesn't give the complete LR code, just the standard 5 character code. LR codes contain an additional 2 character identifier after the main code, which can pinpoint the exact issue. Your code could be related to an electrical, mechanical, or pneumatic issue.
Your best bet is to check everything on the EGR valve, so the electrical connection, the pneumatic pipe and the flap control lever is able to move, and returns to it's normal position after it has been moved. There is a return spring on the control flap, which has been known to fail, resulting in the flap not closing correctly.