Staff Answer
Oct 27, 2026 - 03:51 PM
Diagnostic Trouble Code (DTC) P2055 stands for "Reductant Injection Valve Circuit High (Bank 2, Sensor 1)". This code is triggered when the Engine Control Module (ECM), Powertrain Control Module (PCM), or Reductant Control Module detects that the voltage signal on the Diesel Exhaust Fluid (DEF / AdBlue) injector control circuit for Bank 2 exceeds the expected manufacturer threshold (typically indicating a short to battery voltage or open circuit high condition).
Bank 2 refers to the bank of the engine that does not contain cylinder #1 (on V-style engines) or the secondary SCR/exhaust line on dual-stream exhaust systems. Sensor 1 indicates the upstream reductant injector positioned before the SCR catalyst.
Common Symptoms of DTC P2055
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Illuminated Check Engine Light (CEL): The PCM immediately illuminates the Malfunction Indicator Lamp (MIL).
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DEF / SCR System Warning Message: Dashboard notifications such as "Engine Start Remaining: XX Miles" or "DEF System Fault".
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Speed / Engine Power Limiting (Limp Mode): Vehicle software may restrict top speed or throttle response to comply with emissions regulations.
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Increased Exhaust Emissions: Improper DEF dosing prevents full reduction of nitrogen oxide NOx) gases into nitrogen and water vapor.
Primary Root Causes of DTC P2055
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Defective Reductant Injection Valve (DEF Injector): Internal short circuit to power or open winding inside the reductant injector solenoid on Bank 2.
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Short to Voltage in Wiring Harness: Melted, pinched, or chafed control wires shorting directly to 12V power within the DEF injector harness loom.
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Corroded or Damaged Electrical Connector: Moisture, DEF crystal buildup, bent pins, or oil contamination inside the injector plug harness.
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Faulty Reductant Control Relay / Module: Stuck-closed relay or damaged control driver inside the Reductant Dosing Control Module or PCM.
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Crystallized DEF Contamination: Dried urea buildup causing thermal stress or mechanical binding on the dosing valve coil.
For detailed wiring schematics, DEF system pressure specs, and diagnostic bulletins, visit our full Automotive Diagnostic Fault Code Library.
Watch the video below for a step-by-step visual guide on testing reductant injection circuits and fixing P2055:
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