LLY / LBZ / LMM Duramax Diagnostics

GM Silverado/Sierra 2500HD/3500, 2004.5-2010 — the middle Duramax era: CP3 common rail, first variable-geometry turbo, EGR from the LLY, and a DPF on the LMM (2007.5+). Injector, VGT, EGR and (LMM) DPF codes.

Common symptoms

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…

P0046 — Turbocharger/Supercharger Boost Control A Circuit Range/Performance — LLY / LBZ / LMM Duramax P0046 on LLY/LBZ/LMM Duramax indicates the ECM sees the VGT boost-control circuit operating outside its expected range/performance. On this platform the…
P0093 — Fuel System Leak Detected - Large Leak — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax (2004.5–2010) 6.6L CP3 common rail. Code indicates the ECM sees a rail-pressure drop it can only account for as a…
P0191 — Fuel Rail Pressure Sensor A Circuit Range/Performance — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax (2004.5–2010) with code P0191.
P0192 — Fuel Rail Pressure Sensor A Circuit Low — LLY / LBZ / LMM Duramax P0192 on LLY/LBZ/LMM Duramax (2004.5–2010) means the ECM sees the rail pressure sensor signal voltage below its valid range. Diagnose the sensor circuit first…
P0237 — Turbocharger/Supercharger Boost Sensor A Circuit Low — LLY / LBZ / LMM Duramax P0237 on LLY/LBZ/LMM Duramax means the ECM sees the boost (MAP) sensor signal voltage below its valid range. On this platform the boost sensor is the MAP…
P0403 — Exhaust Gas Recirculation A Control Circuit — LLY / LBZ / LMM Duramax P0403 on LLY/LBZ/LMM Duramax means the ECM has detected a fault in the EGR valve control circuit.
P0405 — Exhaust Gas Recirculation Sensor A Circuit Low — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010. EGR valve position sensor signal voltage is below valid range.
P1093 — Fuel Rail Pressure Low During Power Enrichment — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax (2004.5–2010) when P1093 is set.
P2453 — Diesel Particulate Filter Differential Pressure Sensor A Circuit Range/Performance — LLY / LBZ / LMM Duramax Diagnostic reference for P2453 on LLY/LBZ/LMM Duramax (2004.5–2010).
P2463 — Diesel Particulate Filter Restriction - Soot Accumulation — LLY / LBZ / LMM Duramax P2463 indicates the DPF soot load has exceeded its limit. On LLY/LBZ/LMM Duramax this code applies only to the LMM (2007.5–2010); LLY/LBZ have no DPF. The code…
P003A — Turbocharger/Supercharger Boost Control A Position Exceeded Learning Limit — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax (2004.5–2010) with Garrett GT3788VA VGT.
P0045 — Turbocharger Boost Control Solenoid A Circuit/Open — LLY / LBZ / LMM Duramax P0045 on LLY/LBZ/LMM Duramax indicates an electrical fault in the VGT control solenoid circuit. The Garrett GT3788VA uses engine oil pressure metered by an…
P2563 — Turbocharger Boost Control Position Sensor A Circuit Range/Performance — LLY / LBZ / LMM Duramax P2563 on LLY/LBZ/LMM Duramax indicates the VGT vane position sensor signal is outside its expected range or does not track the commanded position. The Garrett…
P2564 — Turbocharger Boost Control Position Sensor Circuit Low — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010 with code P2564.
P0087 — Fuel Rail/System Pressure Too Low — LLY / LBZ / LMM Duramax Measured fuel rail pressure is below the PCM's commanded value on LLY/LBZ/LMM Duramax 2004.5–2010 with Bosch CP3 common rail and pump-mounted fuel pressure…
P0088 — Fuel Rail/System Pressure Too High — LLY / LBZ / LMM Duramax Fuel Rail/System Pressure Too High
P0089 — Fuel Pressure Regulator Performance — LLY / LBZ / LMM Duramax P0089 on LLY/LBZ/LMM Duramax means the ECM has detected the fuel pressure regulator is not maintaining rail pressure within the expected range on the CP3…
P0101 — Mass or Volume Air Flow Circuit Range/Performance — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010.
P0128 — Coolant Thermostat Below Regulating Temperature — LLY / LBZ / LMM Duramax P0128 on LLY/LBZ/LMM Duramax means the PCM has not seen the engine reach the expected coolant temperature within the expected time. The platform uses a…
P0193 — Fuel Rail Pressure Sensor A Circuit High — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010.
P0201 — Injector Circuit/Open - Cylinder 1 — LLY / LBZ / LMM Duramax P0201 is an electrical fault detected by the ECM in the fuel injector circuit for cylinder 1 on LLY/LBZ/LMM Duramax 2004.5–2010. The code is generic SAE J2012…
P0202 — Injector Circuit/Open - Cylinder 2 — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010. P0202 indicates the ECM has detected an electrical fault in the fuel injector circuit for cylinder 2.
P0234 — Turbocharger/Supercharger Overboost Condition — LLY / LBZ / LMM Duramax P0234 is set when the ECM detects boost pressure above the calibrated maximum for current operating conditions on the LLY/LBZ/LMM Duramax VGT turbo.
P0299 — Turbocharger/Supercharger Underboost Condition — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010.
P0300 — Random/Multiple Cylinder Misfire Detected — LLY / LBZ / LMM Duramax Random/Multiple Cylinder Misfire Detected
P0380 — Glow Plug/Heater Circuit Malfunction — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010.
P0401 — Exhaust Gas Recirculation Flow Insufficient — LLY / LBZ / LMM Duramax Exhaust Gas Recirculation Flow Insufficient
P0402 — Exhaust Gas Recirculation Flow Excessive — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010. Diagnose, do not give step-by-step repair of safety-critical systems.
P0404 — Exhaust Gas Recirculation Control Circuit Range/Performance — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010. EGR present on all; DPF only on LMM; no SCR/DEF on any. Code indicates EGR control circuit operating…
P0420 — Catalyst System Efficiency Below Threshold — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010. P0420 is a generic OBD-II catalyst efficiency code. On this platform the ECM does not run a…
P0670 — Glow Plug Control Module Circuit — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax (2004.5–2010) P0670.
P2002 — Diesel Particulate Filter Efficiency Below Threshold (Bank 1) — LLY / LBZ / LMM Duramax Diagnostic reference for LLY/LBZ/LMM Duramax 2004.5–2010. DPF codes apply to LMM only; LLY/LBZ have no DPF hardware.
P2452 — Diesel Particulate Filter Pressure Sensor A Circuit — LLY / LBZ / LMM Duramax P2452 is a generic OBD-II code for a DPF differential-pressure sensor circuit fault. On the 2004.5–2010 6.6L Duramax family, DPF hardware exists only on the…
P2459 — Diesel Particulate Filter Regeneration Frequency — LLY / LBZ / LMM Duramax P2459 indicates the ECM has counted DPF regenerations more often than expected. On the LLY/LBZ/LMM family this code only applies to the LMM (2007.5–2010) which…