L5P Duramax Diagnostics

GM Silverado/Sierra 2500HD/3500HD, 2017-present — the current Duramax: Denso HP4 common rail, variable-geometry turbo, and the full EGR/DPF/SCR emissions set. Fuel-pressure, VGT, EGR, DPF and DEF codes.

Common symptoms

DEF Warning or Speed Limit Countdown — L5P Duramax L5P Duramax DEF warning and speed-limit countdown diagnostic reference.
Engine Stalls or Dies While Driving — L5P Duramax Diagnostic reference for L5P Duramax 6.6L (2017–present) stalling or dying while driving. Focuses on fuel-system loss of rail pressure that causes sudden…
Frequent DPF Regenerations — L5P Duramax Frequent DPF regenerations on the L5P Duramax means the aftertreatment system is initiating burn cycles more often than normal, typically due to a faulty…
Hard Start or Long Crank — L5P Duramax Diagnostic reference for hard start/long crank on 2017–present 6.6L L5P Duramax. Focuses on fuel supply/rail pressure and cold-start glow system faults that…
Loss of Power or Limp Mode — L5P Duramax Loss of power or limp mode on the L5P Duramax is a protective derate triggered by the ECM when a critical system fault is detected. The engine limits torque…
Rough Idle and White Smoke on Cold Start — L5P Duramax A diagnostic reference for the L5P Duramax (2017–present) when the engine idles rough and produces white smoke on cold start, typically clearing as the engine…

P0089 — Fuel Pressure Regulator 1 Performance — L5P Duramax Diagnostic reference for L5P Duramax (2017–present) 6.6L with a Denso HP4 high-pressure pump and fuel pressure control valve. Rail pressure is monitored by a…
P2032 — Exhaust Gas Temperature Sensor Circuit Low Bank 1 Sensor 2 — L5P Duramax P2032 on L5P Duramax indicates the bank 1 sensor 2 exhaust gas temperature sensor signal voltage is below its valid range. On this platform the fault is…
P2047 — Reductant Injector Circuit/Open Bank 1 Unit 1 — L5P Duramax Diagnostic reference for L5P Duramax (2017–present) P2047.
P20B9 — Reductant Heater A Control Circuit/Open — L5P Duramax Diagnostic reference for L5P Duramax (2017–present) when ECM reports an open/fault in DEF reductant heater A control circuit. Focus on electrical integrity of…
P2201 — NOx Sensor Circuit Range/Performance Bank 1 Sensor 1 — L5P Duramax Diagnostic reference for P2201 on L5P Duramax (2017–present).
P229F — NOx Sensor Circuit Range/Performance Bank 1 Sensor 2 — L5P Duramax Diagnostic reference for L5P Duramax (2017–present) 6.6L.
P242F — Diesel Particulate Filter Restriction - Ash Accumulation — L5P Duramax Diesel Particulate Filter Restriction - Ash Accumulation
P2463 — Diesel Particulate Filter Restriction - Soot Accumulation — L5P Duramax P2463 indicates the DPF soot load has exceeded its limit on the L5P Duramax. The code is set when the ECM estimates or measures excessive restriction from…
P2564 — Turbocharger Boost Control Position Sensor A Circuit Low — L5P Duramax Diagnostic reference for L5P Duramax (2017–present) P2564.
P003A — Turbocharger/Supercharger Boost Control A Position Exceeded Learning Limit — L5P Duramax Diagnostic reference for L5P Duramax (2017–present) with code P003A.
P203F — Reductant Level Too Low — L5P Duramax Diagnostic reference for P203F on L5P Duramax (2017–present).
P2563 — Turbocharger Boost Control Position Sensor A Circuit Range/Performance — L5P Duramax Diagnostic reference for L5P Duramax (2017–present) P2563.
P0087 — Fuel Rail/System Pressure Too Low — L5P Duramax Measured fuel rail pressure is below the PCM's commanded value on the L5P Duramax (2017–present 6.6L). The L5P uses a Denso HP4 high-pressure pump with a fuel…
P0088 — Fuel Rail/System Pressure Too High — L5P Duramax Measured fuel rail pressure exceeds the commanded value on the L5P Duramax (2017–present 6.6L). The Denso HP4 high-pressure pump regulates rail pressure via…
P0090 — Fuel Pressure Regulator Control Circuit — L5P Duramax Diagnostic reference for P0090 on L5P Duramax (2017–present).
P0101 — Mass or Volume Air Flow Circuit Range/Performance — L5P Duramax Mass or Volume Air Flow Circuit Range/Performance
P0128 — Coolant Thermostat Below Regulating Temperature — L5P Duramax P0128 is a generic thermostat rationality / low coolant temperature code. On the L5P Duramax (2017–present 6.6L) it typically presents as a mechanical…
P0201 — Injector Circuit/Open - Cylinder 1 — L5P Duramax Diagnostic reference for P0201 on L5P Duramax (2017–present).
P0234 — Turbocharger/Supercharger Overboost Condition — L5P Duramax P0234 on the L5P Duramax means the ECM has detected boost pressure exceeding the maximum allowed for current conditions. The L5P uses a variable-geometry turbo…
P0263 — Cylinder 1 Contribution/Balance Fault — L5P Duramax P0263 on L5P Duramax means the PCM has detected cylinder 1 output deviating from the others. On this platform the fault is an injector or compression issue for…
P0299 — Turbocharger/Supercharger Underboost Condition — L5P Duramax Boost pressure is below the minimum expected for current conditions. On L5P Duramax the turbo is a variable-geometry turbo (VGT) with an electric actuator and…
P0380 — Glow Plug/Heater Circuit Malfunction — L5P Duramax Diagnostic reference for P0380 on L5P Duramax (2017–present).
P0401 — Exhaust Gas Recirculation Flow Insufficient — L5P Duramax Diagnostic reference for L5P Duramax (2017–present) P0401.
P0420 — Catalyst System Efficiency Below Threshold — L5P Duramax Diagnostic reference for L5P Duramax (2017–present) when generic OBD-II code P0420 is stored. On this diesel platform the code is not a true catalyst monitor…
P042E — Exhaust Gas Recirculation Control Stuck Open — L5P Duramax Diagnostic reference for P042E on L5P Duramax (2017–present).
P0670 — Glow Plug Control Module Circuit — L5P Duramax Diagnostic reference for P0670 on L5P Duramax (2017–present).
P2002 — Diesel Particulate Filter Efficiency Below Threshold (Bank 1) — L5P Duramax Diagnostic reference for L5P Duramax 2017–present.
P204F — Reductant System Performance — L5P Duramax Diagnostic reference for P204F on L5P Duramax (2017–present).
P20E8 — Reductant Pressure Too Low — L5P Duramax Reductant Pressure Too Low
P20EE — SCR NOx Catalyst Efficiency Below Threshold (Bank 1) — L5P Duramax Diagnostic reference for L5P Duramax 2017–present 6.6L. P20EE indicates the SCR NOx conversion efficiency monitor is below threshold. Diagnose by confirming…
P2452 — Diesel Particulate Filter Pressure Sensor A Circuit — L5P Duramax Diesel Particulate Filter Pressure Sensor A Circuit
P2459 — Diesel Particulate Filter Regeneration Frequency — L5P Duramax Diagnostic reference for P2459 on L5P Duramax (2017–present).
P2BAD — NOx Exceedance — Root Cause Unknown — L5P Duramax NOx Exceedance — Root Cause Unknown