P218F: Reductant performance uses correlation between dosing, pump effort, and pressure

P218F is reductant-system performance. Ford places it in a delivery/clogging plausibility monitor, but its actual evidence is correlation among commanded injection rate, pump duty cycle, and DEF pressure behavior. The code is not a direct visual finding that a particular line is blocked.

Dosing and pressure regulation must be qualified

The listed entry state is active SCR dosing with reductant-pressure control error between −0.5 and +0.5 bar. Conditions must persist for at least five seconds, and pressure-sensor low/high diagnostics must be satisfactory.

Ford describes a correlation error greater than 0.15 involving injection command and pump duty, together with an integrated pressure/command correlation condition. The second threshold is not numerically published here, so this summary cannot be turned into a complete stand-alone calculation from a few scan-tool snapshots.

Related trends matter more than one value

A useful investigation preserves the time relationship between dosing requests, pump effort, and pressure response. A pressure reading close to target does not alone prove correct delivery, because the monitor looks at how the signals correlate while dosing.

Conversely, the performance code does not identify the exact restriction or establish a failed pump or injector. Ford’s summary supplies a system-response check with valid-input prerequisites. The applicable service procedure is needed to separate delivery-path, control, and measurement causes before any reductant component is cleaned or replaced.

Source and applicability

This explanation follows Ford’s 2023–2024 diesel OBD summary. Match the vehicle’s engine and calibration before applying these monitor values; a generic code alone does not establish fitment. Ford PDF, page 84.