DPD lights switches on seconds after turning the engine on

A fault with the diesel particulate diffuser has been detected by the engine control module. You would need a diagnostic scan to retrieve the trouble codes to proceed further. It could be due to partial clogging of exhaust system or any leakages.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Retrieve the trouble codes and let us know what it is.

Thank you. Will get back to you when I retrieve the trouble codes.