Emissions

P2051 — Reductant (DEF) Injector Circuit High

Severity: medium Drive with care, to a shop

What P2051 means

The engine or SCR control module drives a reductant (DEF/AdBlue) injector that sprays urea solution into the exhaust to reduce NOx. P2051 sets when the voltage in the injector control circuit is higher than expected. Typical causes are an open circuit, a failed injector or a control module fault. The SCR system is disabled or works incorrectly as a result.

Symptoms

  • Check engine light or SCR/AdBlue warning on
  • SCR system inoperative
  • Power or torque reduction, especially on heavy-duty diesels
  • Possible start countdown before a no-start lockout
  • Increased NOx emissions

Possible causes

  1. Open circuit in the injector control wire
  2. Failed DEF dosing injector
  3. Corroded or loose connector
  4. Damaged wiring harness
  5. SCR or engine control module fault

How to diagnose

  1. Read all codes and freeze frame data and look for other SCR codes
  2. Check DEF level, quality and dosing system status data
  3. Inspect the injector, lines and heater operation
  4. Inspect SCR connectors and wiring for opens, corrosion and damage
  5. Measure injector resistance and control circuit voltage
  6. Test circuit continuity back to the control module
  7. Check for manufacturer service bulletins and software updates

Common fixes

  • Repair open or damaged wiring and clean connectors
  • Replace the DEF dosing injector
  • Update control module software
  • Replace the SCR control module if confirmed faulty
  • Clear codes and verify the dosing system operates

Questions and answers

Can I drive with code P2051?

For a short time, yes, but the SCR system is not working. Power limiting or a start lockout after a countdown is possible, so repair it soon.

What does a high circuit signal on the DEF injector mean?

The control unit sees too much voltage on the injector control line. It is most often an open circuit or a bad injector, and less often a control module problem.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.