2016 4N14 outlander 156K kms. DPF and turbo replaced last year, dpf was blocked pressure pipes also so no indication of a problem until failure, was noisy tbh. Anyhow, new DPF and recon turbo were fine until a few months back, then p0420 light came on. Had it with Mitsubishi garage and found cracked manifold and leaking injector seal, they were resolved. I found egr issue, egr bank 1 monitor failed and I removed and cleaned egr and throttle body, cleaned those 2 weeks ago. Used scan tool to indicate a new DPF, did a forced regen and all was ok until the car did a regen itself after around 400km and fault code again. When I cleaned the egr I didn’t have a vacuum gun so only did a surface clean on the vacuum valve. Since the p0420 returned the egr bank 1 monitor failed, then I retested a few times and it worked….. the replacement dpf wasn’t Mitsubishi supplied. I’m thinking the root cause of the original problem is not solved or something damaged the new dpf after 6 months around 7000 km or the cat needs a clean…..

Next step I’m thinking is to remove inlet manifold and clean and maybe remove egr again and try to clean vaccum valve.

The question is, where to look next?

Appreciate any feedback on this….