LLY-LMM Duramax Symptoms

Common LLY-LMM Duramax symptoms, what usually causes them, and how to narrow them down.

• Black Smoke Under Load — LLY / LBZ / LMM Duramax Black smoke under load on LLY/LBZ/LMM Duramax (2004.5–2010) is a symptom of too much fuel for available air. The platform uses a Garrett GT3788VA VGT turbo…
• Frequent DPF Regenerations (LMM) — LLY / LBZ / LMM Duramax Diagnostic reference for frequent or constant DPF regenerations on LLY/LBZ/LMM Duramax (2004.5–2010).
• Hard Start or Long Crank — LLY / LBZ / LMM Duramax Diagnostic guide for hard start or long crank on LLY/LBZ/LMM Duramax 2004.5–2010.
• Loss of Power or Limp Mode — LLY / LBZ / LMM Duramax Loss of power or limp mode on LLY/LBZ/LMM Duramax (2004.5–2010) — diagnostic reference for VGT turbo, fuel system and, on LMM only, DPF-related causes.
• Overheating When Towing — LLY / LBZ / LMM Duramax A concise diagnostic reference for LLY/LBZ/LMM Duramax (2004.5–2010) that overheats under load, especially while towing. Focuses on cooling system capacity and…
• Rough Idle or Misfire — LLY / LBZ / LMM Duramax A rough idle or misfire on LLY/LBZ/LMM Duramax (2004.5–2010) usually points to an injector — a circuit or connector fault on one cylinder, or a worn or leaking…
• White Smoke or Rough Running on Cold Start — LLY / LBZ / LMM Duramax White smoke or rough running that clears as the engine warms on LLY/LBZ/LMM Duramax 2004.5–2010 usually means cold-start combustion is incomplete. The platform…