Have a 2016 Colorado diesel. Had a couple issues where service diesel exhaust light came on but reset by itself. Had 121,000 miles and on 7/11/19 got poor DEF quality warning. Tried adding new DEF no luck. Went into limp mode 4MPH. Had to be towed. Took to dealer and informed my extended warranty out by 2000miles. They charged me $150 to diagnose and were able to reset. They drained and tested my DEF it was Good. Told them I needed fuel filters changed but they forgot to change. Today Poor Def quality warning came back and is in transition to limp mode. Does anyone think it could be the fuel filter causing the problem? Heading to dealer in the morning.