P218F: Reductant No Flow Detected

P218F means the SCR system is dosing on paper, but nothing reaches the exhaust: the expected link between dosing commands, pump effort and line pressure is missing. Ford's 2023 diesel summary, which calls the test a reductant delivery check for clogging, runs it while dosing with the pressure error inside 0.5 bar for 5 s. It fails when the pressure barely reacts to changes in the injection rate and the mix of rate and pump duty misses its model by more than 0.15. Ford also lists it for the 6.7 L Power Stroke (18-2127, PCM update). Nissan reflashed Titan XD trucks with the Cummins 5.0 L V8 when P218F appeared at 0 °C or below. VW says P218F can stay after repairs on 2.0 TDI cars until a leak in the DEF line is fixed. Pressure codes are P20E8/P20E9.

Symptoms

• Check engine light with a DEF or emission system warning
• Restart countdown or speed limitation if the fault persists
• DEF consumption lower than usual
• White crystalline deposits at the dosing valve or line joints

Most likely causes

• Dosing valve or its nozzle crystallised and blocked
• Leak in the DEF line between pump and dosing valve
• Partly frozen line in frost or control software that needs an update
• Worn DEF pump that cannot keep up delivery

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the AdBlue/DEF level and quality, and do not add additives or water
2. Look for white crystals around the injector and the tank
3. Check connectors and heaters with the scanner
4. Run the dosing test available on your diagnostic tool
5. Replace parts only when the test points to that component

Good to know

• Repair difficulty: hard
• It can trigger limp mode.
• It affects emissions.

What each character of P218F means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 1: Air and fuel
• 8F: Specific fault in that system

Frequently asked questions

Can I keep driving with code P218F?

Deal with it soon. If the instrument cluster shows a countdown, the car may not restart once it reaches zero.

What causes code P218F?

The most common causes are: dosing valve or its nozzle crystallised and blocked; leak in the DEF line between pump and dosing valve; partly frozen line in frost or control software that needs an update.

Related codes

• P20E8Reductant Pressure Too Low
• P20E9Reductant Pressure Too High
• P208BReductant Pump A Control Performance/Stuck Off
• P208EReductant Injection Valve Stuck Closed (Bank 1 Unit 1)
• P204FReductant System Performance (Bank 1)
• P249CExcessive Time To Enter Closed Loop Reductant Injection Control
• P2047Reductant Injection Valve Circuit/Open (Bank 1 Unit 1)

Sources

• fordservicecontent.com: obd summary diesel 2023
• static.nhtsa.gov: MC 10116290 9999
• static.nhtsa.gov: MC 10128051 9999
• static.nhtsa.gov: MC 10137123 9999

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.