Used Duramax 3.0 (LM2/LZ0): what to check before you buy

1Before you go

Run the VIN and ask for the paperwork on the campaigns below: a done recall or program is a solved problem, an open one is a free repair the seller has not had done.

• Run the VIN

  It confirms the engine and lists the campaigns for that model year. Whether a recall is still open on this VIN: nhtsa.gov/recalls.

• Safety recalls on this engine
  • 25V-619 · 2021-2024 · Fuel system, diesel
  • 24V-797 · 2020-2022 · Power train
• Programs, extended coverages and emissions recalls
  • N252508341 · Special coverage / warranty extension

  Plus 2 service bulletins on the recalls page.

2Cold start and idle

Ask the seller not to start or warm the engine before you arrive. Most of these only show on a cold engine; then let it idle and listen.

• Extended crank / long-crank no-start (air intrusion, check valve, cam wheel)
  • after sitting 2-3 days the engine cranks long before starting; a key-on prime cycle before cranking helps
  • long cranking right after a fuel filter change (air trapped in the system)
  • worst case: crank-but-no-start until the system re-primes
• EGR system failures: valve, cooler, wiring (derate-prone)
  • EGR cooler failure: slow coolant loss with no visible puddle, sometimes white smoke on cold starts

3Scan for codes

A basic OBD-II reader shows stored and pending codes; on a diesel ask a shop for a full scan if you can. These are the codes our records tie to known failures on this engine.

What a code means on each engine: trouble codes by engine.

4Hood up and underneath

Engine off, in daylight, with a flashlight.

• Turbo and boost-path faults (coolant line, charge air)
  • coolant loss traced to the hard coolant line to the turbo (community-documented)

  To confirm: smoke-test the boost path before condemning the turbo (underboost is often a pipe/clamp)

5Test drive

At least 20 minutes, including a highway run and a hill or a load if you can.

• Coolant flow control valve failure (active thermal management)
  • constant high-running radiator fan, fluctuating temperature, 'Engine Power Reduced' message
  • P1098 (and neighboring circuit codes); temperature spikes past 210F in traffic
• DEF system faults: tank heater, pump/quality (speed-limited derate)
  • 'Exhaust Fluid System' / DEF quality warnings, countdown to speed limitation
  • hard 5-mph derate when ignored; NOx codes accompany tank-side heater/pump faults
• DPF regeneration and ash-loading faults
  • regen not completing / frequent regens, DPF differential-pressure codes
  • power loss / derate when ash-loaded beyond limits
• EGR system failures: valve, cooler, wiring (derate-prone)
  • check engine / 'Service Emission System' message, often with a speed limitation (65 mph) derate
• LZ0 crankshaft thrust bearing failure (GM bulletin 25-NA-307)2025-2026
  • noise from the bellhousing area, oil-pressure code P06DD, 'Reduced acceleration' message
• NOx sensor / SCR efficiency codes
  • P20EE (NOx catalyst efficiency) and NOx sensor circuit codes, CEL
  • may accompany the DEF derate ladder when SCR efficiency reads low
• Turbo and boost-path faults (coolant line, charge air)
  • underboost/overboost codes (P0299 family), smoke, power loss

What it costs if you find it

Parts budgets from our repair recipes for this engine: Dave's Auto Center's prices where Dave's lists the part, approximate OEM and maker catalog prices (rounded) for the rest; labor not included. A campaign listed next to a failure may make the repair free on a covered truck: check it by VIN.