Recipe - GM 3.0L Duramax LM2/LZ0 I6 (2020+)
Specific Fix build
Reliability tier: verified - verify before ordering, see /disclosure/
DEF tank-side service for the 3.0L Duramax (mode DEF system faults: tank heater, pump/quality (speed-limited derate)): the 'Exhaust Fluid System' warnings walk up a derate ladder to 5 mph. Work cheap first: quality fluid and codes, then the controller, then the tank assembly (the heater/pump/level unit). Tank windows split by body and year - three carded numbers cover the line.
Parts
- DEF refill - fresh API-certified fluid (service item, all 3.0L Duramax) - fresh API-certified DEF first - contaminated fluid mimics hardware (qty 1)
- 3.0L Duramax DEF Controller (GM 85514348) - tank-side controller (85514348, pickups 2020-2023) - the cheap brain (qty 1)
- 3.0L Duramax DEF Tank Assembly, pickups 2020-2022 (GM 86790695) - pickup tank 2020-2022 (86790695) (qty 1)
- 3.0L Duramax DEF Tank Assembly, SUVs 2021-2023 (GM 86772598) - SUV tank 2021-2023 / pickup 2022-2023 (86772598) (qty 1)
- 3.0L Duramax DEF Tank Assembly, pickups 2022-2024 (GM 87867197) - pickup tank 2022-2024 (87867197) (qty 1)
Install order
- read codes together: tank-side heater/pump codes before NOx codes; test DEF quality
- drain and refill with fresh DEF - retest before parts
- controller if the codes point at the tank electronics
- tank assembly when elements test open: drop the tank, swap the assembly, refill and prime
Expected outcome
Parts budget
About $110-$500 in parts. It depends on what the diagnosis finds; each option below is what you buy together. Prices marked "at Dave's" are Dave's Auto Center's, the same as in his store; the others are approximate prices from OEM and maker catalogs, rounded (a manufacturer's list price can run higher). Parts only, no labor.