Suburban Diesel Fuel Filter Issue

That sounds familiar. My nightmare was with a 2016 Audi Q7. The symptoms you describe sound similar to an issue I had with my fuel filter heater. The error was also stored in the error memory. The diagnostic pointed towards a faulty heater, or possibly the wiring connection to it. From what you describe, I understand you've already had a look. Did you check the plug connection of the fuel filter heater?

I hadn't really considered the heater! I did have a quick look at the fuel filter itself, checking for leaks. When you say 'plug connection,' do you mean where the wiring harness plugs into the fuel filter assembly, or somewhere else along the fuel line? Was it visibly corroded or damaged, or did you need a multimeter to diagnose it correctly?

I meant the plug connection to the fuel filter heater itself. In my case, it wasn't visibly corroded – everything looked clean. I only found out thanks to workshop diagnostics. Given the mileage, you might indeed have a wiring problem there. Honestly, you are better off having a technician look for such a small component. At least they can measure the connections and check the wiring, and you don't have to crawl around in the dirt.

Thanks a lot for the tip about the plug connection! Took it to a local shop and turns out you were spot on. There was a defective cable / plug connection. Cost me 95€ and now the car runs fine. I appreciate you pointing me to the right direction!