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Home / DTC / P20F5 — Reductant Consumption Too High

P20F5 — Reductant Consumption Too High

Detailed page for trouble code P20F5.

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Code

P20F5

Generic P — Powertrain

Reductant Consumption Too High

Brand: Generic
Type: P — Powertrain
Views: UK: 12 EN: 50 RU: 17
AI status
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Page language: EN

Causes

  • External leak in reductant (DEF) supply, tank, lines, fittings, or injector
  • Stuck-open or over‑dosing reductant injector/metering valve
  • DEF pump over‑delivering or faulty pressure/regulation
  • Contaminated or incorrect reductant (wrong fluid, high chloride/humidity)
  • Faulty DEF level/flow sensors or NOx sensors giving incorrect feedback
  • Wiring harness or connector faults to pump, injector or sensors (short to power/ground)

Symptoms

  • Rapidly decreasing DEF level (higher-than-normal refill frequency)
  • SCR system or DEF warning lamp illuminated; possible MIL
  • Reduced NOx conversion efficiency or elevated tailpipe NOx readings
  • Possible limp/derate condition depending on manufacturer strategy
  • Crystallization or white residue around fittings, lines, tank, or injector area
  • Unusual pump noise or heater fault messages

What to check

  • Read and record all freeze‑frame and related trouble codes; check pending codes
  • Visually inspect tank, lines, fittings, injector and SCR components for wetness, white crystalline deposits, corrosion or physical damage
  • Check DEF quality: clarity, color, contamination, smell; verify correct product (ISO 22241 compliant)
  • Scan for live PIDs: reductant flow rate, commanded vs actual injector duty/pulse, pump current/pressure, DEF tank level, DEF temperature, NOx sensor readings
  • Inspect wiring and connectors for corrosion, damage, chafing or loose pins at pump, injector and sensors
  • Pressure‑test or flow‑verify metering valve and pump per manufacturer procedure

Signal parameters

  • Reductant flow rate (L/min) — commanded vs actual
  • Injector/ metering valve duty cycle or pulse width (%)
  • Pump current (A) and/or pump pressure (bar or kPa)
  • DEF tank level voltage or resistance (V or ohms)
  • DEF temperature (°C) — if heater operating, check status
  • NOx sensor output (V or ppm) upstream/downstream

Diagnostic algorithm

  1. Verify code with scan tool, record freeze frame and related codes. Do not replace parts without verification.
  2. Inspect for external leaks and crystallization around tank, lines, injector and fittings. Repair any physical leaks and retest.
  3. Check DEF quality: drain and sample if contamination or wrong fluid is suspected. Replace fluid and clean tank if contaminated.
  4. With scan tool, compare commanded reductant dose vs measured parameters (flow, injector duty, pump current). Note discrepancies.
  5. Test pump operation: verify correct pressure/flow and electrical current draw; inspect pump relay/fuse circuits.
  6. Test metering valve/injector: verify it opens/closes and measure flow while commanding doses; replace if mechanically stuck or over‑dosing.

Likely causes

  • Leaking supply hose or injector seal (most common)
  • Stuck or mechanically failed reductant injector / metering valve
  • DEF contamination or use of non‑specified fluid
  • Failed pump or pressure regulator causing over‑delivery
  • Faulty flow/level/NOx sensors or wiring giving incorrect measurements

Fault status

⚠️ Status
ECM reports reductant consumption higher than expected. Inspect SCR dosing components (tank, lines, pump, injector/metering valve), DEF quality, sensors and wiring. Repair confirmed faults and verify consumption returns to specification.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-4 hours

Similar codes

P20F0 P20F1 P20F2 P20F3 P20F4 P20F6
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