New to me stock 2009 6.7 Bluetech 4x4 is smoking black smoke. Didnt notice when i test drove it but when following behind its blowing (not a lot) black smoke. Not just at acceleration seemingly random light to heavy puffs of smoke and also when accelerating.

 

Are you sure it's all stock?
If it's got all the exhaust components then you've got a damaged particulate filter.

 

so now ive got 2 codes that just came up. P2002 (DPF efficiency below threshold) and P2509 (ECM/PCM power input signal intermittent. Sounds expensive! Where to start?