2019 Peterbilt 579 - wire issue

rn · Dec 7, 2025 02:36

Truck won’t do a regen or forced regen; Peterbilt dealer initially diagnosed VGT isssue but said it $5k and can’t guarantee his work and there could be other issues; paid $3000 to replace VGT yet truck is still in derate. now mechanic says it could be a wiring issue or other codes so basically they don’t know the exact issue. if anyone has expertise or experience in this please leave a comment. Thank you

Comments (3)

john

paccar emissions systems from 2018-2020 are notorious for NOx sensors failures. one bad sensor leads to Regen disabled.

john

and ecm does not care if anything else is good. also, check for broken wires near DPF differential pressure sensor. also check for molten wires near turbo or after treatment. I hope this help brother.

owneroperatorlife

Ok, so basically the ECU is giving incorrect readings—which I’m sure you already know—so here’s what to do: disconnect the differential pressure sensor and its hoses. Check whether soot is blocking them, because this is an extremely common issue on these trucks.It could also be a NOx sensor logic lockout. Make sure to inspect your wiring harnesses too; they can get burnt or damaged, and that’s also very common on these trucks.Honestly, new trucks are getting worse every year, so it’s no surprise this kind of thing happens.