3/4 and 1 ton trucks.
Diesel mostly, gas welcome.
2020 Silverado 2500 HD, L5P, Allison 10 speed, 64,000. hay in the winter, a 20 ft bumper pull flatbed the rest of the year.
friday coming back from Glendive it threw "Exhaust Fluid Quality Poor, Service Emission System" and started a countdown in miles on the dash. DEF came from the pump at the Cenex in town, same as always. dealer in Miles City can't get it in until the 24th. my cheap reader shows P20EE and P2200. what am i looking at, and how scared of the countdown should i be?
P2200 with P20EE on an L5P is nine times out of ten the upstream NOx sensor reading garbage. the ECM then decides the SCR isn't converting and blames the fluid. we swap a lot of upstream sensors between 50 and 90k. the part runs 400 to 600 depending where you buy it.
do the 30 dollar test first though. a DEF refractometer should read 32.5 percent. if the fluid is right, it is the sensor. and the countdown is real, it takes you to 55 and then to limp speed. don't try to beat it to Billings.
and for anybody landing here from a search. the fix for a bad NOx sensor is a NOx sensor. somebody will tell you to "just delete it". on a truck that is registered and driven on public roads that breaks federal law, the EPA has been going after the shops and the tuner sellers hard, and a deleted truck is a headache to sell afterward. it also throws away whatever emissions warranty you had left, which on some of these parts runs longer than the powertrain. read the warranty booklet before you pay for a sensor.
borrowed a refractometer off the neighbor who runs a Peterbilt: 32.2. fluid is fine. asked the dealer about the booklet thing and they are checking whether the upstream sensor falls under the longer coverage. countdown is at 200 miles and i am driving the old 7.3 till then.
my brother had the same pair of codes on his 2019 3500 L5P. upstream sensor. his came back two days after the fix and it turned out the connector on the new sensor was not clicked all the way home. push on it before you leave the lot.
done. upstream NOx sensor, covered under the emissions warranty, and they dropped the diag fee once it came back a warranty part. 11 days without the truck, which was the real cost. connector clicked, i checked. the refractometer lives in the glovebox now.