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Home / DTC / P218F — Reductant No Flow Detected

P218F — Reductant No Flow Detected

Detailed page for trouble code P218F.

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Code

P218F

Generic P — Powertrain

Reductant No Flow Detected

Brand: Generic
Type: P — Powertrain
Views: UK: 14 EN: 70 RU: 37
AI status
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Page language: EN

Causes

  • Empty or low reductant tank
  • Failed reductant pump or pump motor
  • Blocked or restricted dosing line, filter, or injector (crystals/contamination)
  • Stuck or leaking dosing valve/injector
  • Faulty reductant flow sensor or missing flow sensor signal
  • Open/short or corroded wiring and connectors to pump, valve, or sensor

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated and related DTC present
  • Reduced emission system performance; possible limp mode on some systems
  • No audible pump operation when DEF system is commanded
  • Visible crystallized urea around tank, lines, filter, or injector
  • Exhaust system may show increased NOx or fail emissions tests

What to check

  • Read freeze frame and live data with a capable scan tool; confirm P218F and any related codes
  • Check reductant tank level and condition (contamination, crystals)
  • Listen for pump operation when the system is commanded; check for pump noise
  • Inspect wiring harnesses and connectors for damage, corrosion, or water intrusion
  • Measure voltage and ground at pump connector with key ON and during command
  • Check resistance and continuity of flow sensor and injector/valve circuits

Signal parameters

  • Pump supply voltage: ~Battery voltage when commanded (nominal 12 V system)
  • Pump current draw: varies by model (typically ~1–7 A when running) — abnormal low or zero indicates no pump operation
  • Flow sensor output: pulse or frequency signal proportional to flow (may be counted as pulses/min or Hz)
  • Injector/dosing valve command: duty cycle or on/off status from ECM
  • Flow reading expected: small but measurable flow during dosing events (model-dependent)
  • Line pressure: low-pressure system; some systems monitor pressure or injector back-pressure

Diagnostic algorithm

  1. Use a scan tool to confirm P218F and record freeze frame/live data while commanding a dosing event.
  2. Verify reductant tank level and inspect for contamination, crystallization, or foreign matter. Refill if low with correct fluid.
  3. Visually inspect the entire reductant system: tank, filter, lines, connectors, heaters, and dosing injector/outlet for damage or crystals.
  4. With ignition on, command the reductant pump on via scan tool and listen/feel for operation. Measure pump supply voltage and ground; compare to battery.
  5. Measure pump current during commanded operation. Zero or very low current suggests open circuit, bad pump, or relay/fuse issue.
  6. Check continuity and resistance of pump, flow sensor, and injector circuits. Repair any wiring faults or corroded connectors.
  7. Monitor flow sensor output during a commanded dose. No pulses or implausible values point to sensor or actual no-flow condition.
  8. If pump and wiring test good but no flow, inspect/remove dosing injector and filter for clogging; clean or replace as required.
  9. If components bench-test OK, check for air locks or trapped air in lines; follow manufacturer bleed procedure.
  10. After repairs, clear codes and perform a confirmed drive/soak cycle or commanded dosing to verify flow and that P218F does not return.
  11. Safety note: DEF/urea crystallizes and can cause skin/eye irritation — wear gloves and eye protection; avoid contamination of fluid.

Likely causes

  • Pump failure (electrical or mechanical)
  • Blocked dosing injector or filter due to crystallized urea
  • No power or poor connection to pump or flow sensor
  • Faulty flow sensor or incorrect sensor readings
  • Empty tank or air in the supply line

Fault status

⚠️ Status
Reductant dosing expected but no flow detected during commanded operation; emission dosing system fault.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

P20F0 P20F1 P20F2 P20F3 P20F4 P20F5
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