P218F code meaning
Reductant No Flow Detected
Powertrain system Generic code P21xx codes Check engine light
What P218F means
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.
P218F at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairAfter a drive cycle
Symptoms of P218F
- 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
Common causes of P218F
- Most likelyDosing valve or its nozzle crystallised and blocked
- PossibleLeak in the DEF line between pump and dosing valve
- PossiblePartly frozen line in frost or control software that needs an update
- Less likelyWorn DEF pump that cannot keep up delivery
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant metering unitReductant pumpReductant injection valve
What each part of P218F means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 1 | Area: fuel and air metering. |
| 8F | The exact fault in that area. |
What to do next
- Note P218F and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P218F
What does P218F mean?
P218F means "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. It is a generic code, so it means the same on every make.
Is it safe to drive with P218F?
Drive gently and only to a workshop. With P218F the car can go into limp mode (reduced power) to protect itself.
Will P218F fail an emissions test?
Yes, it can. P218F is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P218F to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P218F clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.