DEF, DPF and EGR: how do you check a repo diesel's emissions system is intact from photos, before you bid

good question to ask before and not after. here is how i go through photos, in the order i look:

• the exhaust from under the truck. on all three brands from 2019 on you should see the DOC/DPF can and then the SCR can with the DEF doser between them. stock clamps, factory heat shields. a 4 or 5 inch pipe straight back with no cans is a delete. cans with fresh welds or band clamps that do not match are a warning.
• the tailpipe. a big polished aftermarket tip is not proof of anything, but it makes me look harder at everything else.
• the cluster photo with the engine running. DEF gauge showing a level, no check engine light, no "service emissions system" or "exhaust fluid quality" message. if the only cluster photo is with the engine off, the lights tell you nothing.
• the dash, the A pillar, the windshield and the OBD port under the dash. a monitor or tuner screen stuck up there, or a cable running down to the port, means somebody was in the computer.
• under the hood, the EGR cooler and valve plumbing should be there. block off plates and a missing cooler are obvious once you know where to look.

and decode the VIN, then compare to what is in the photos. a truck listed as stock with aftermarket parts all over it is something you note before you bid.

this is close to exactly what i did on mine. the photo that sold me was one from under the truck showing both cans and the clamps. the running cluster photo showed the DEF gauge at half and nothing lit.

one thing i would add. the 30 day money back guarantee at conaways is for a lot that turns out to be materially misrepresented. a truck sold as stock that arrives deleted, i would expect that to count, but i would rather not ever have to find out, which is why the photo homework matters. and a scan after delivery is cheap, i paid 145.

Michigan does not do emissions inspections on vehicles at all, so you could register a deleted truck there without anyone stopping you. do not let that make you comfortable. it is still against federal law to drive it that way, a lot of shops will not work on one, and when you go to sell it you are selling it to a much smaller group of people for a lot less money. and if you ever move to a state with inspections, it is your problem then.

marco's list is the right one. i would add: if the listing has a video of a cold start, watch the exhaust. a stock truck with a working DPF should have basically clean exhaust once it is running, no black puff when it revs.

did the same zoom routine on my Silverado. one limitation nobody can get around: you cannot see soot load or how often it regenerates from a photo, or whether somebody flashed a tune and then put the stock file back. the photos from conaway's were good enough to rule things out, they just cannot prove everything is perfect inside. go in expecting to pay a diesel shop for a scan the first week, and set some money aside in case it needs a sensor.