Powertrain, generic (extended)

P218F Reductant No Flow Detected

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

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.

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

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

Repair estimate

DifficultyHardWorkshop job

Parts and labour€0–1,500

Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reductant metering unitreductant pumpreductant injection valve

References: fordservicecontent.com, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.