P218F: Reductant No Flow Detected
What to do
Check the reductant tank level yourself first, and say when it was last filled. It sounds obvious, but a level sensor reporting fluid that is not actually there produces exactly this fault.
Mention the weather. In cold conditions this is very often frozen fluid rather than a failed part — the fluid freezes at about −11°C — and the real fault is then a heater rather than anything in the dosing system.
Ask whether the injector can be cleaned rather than replaced. The usual cause is dried reductant blocking it, that dissolves in warm water, and the part is expensive.
Do not leave it. With nothing being dosed, the emissions system escalates towards limiting your speed and eventually refusing to restart the engine.
What this code means
The system commanded reductant dosing and detected none leaving.
This is the bluntest code in the reductant family and it is the easiest to read: the module asked for fluid and nothing moved. Not too little — none.
That absoluteness narrows the causes usefully, because a partial restriction produces a pressure or consumption code instead. No flow at all means the path is completely closed somewhere, and there are only a handful of places it can be.
- A crystallised injector, jammed shut by dried urea deposits. This is the commonest cause by some margin.
- Frozen fluid, which is the seasonal answer and points at a heater fault rather than a dosing one. In cold weather, check the heater circuits before touching the dosing hardware.
- A blocked filter or a pump that is not running.
- An empty tank, which sounds obvious and is worth confirming rather than assuming — a level sensor reporting fluid that is not there produces exactly this.
The consequence is immediate and legally mandated. With no reductant reaching the exhaust, nitrogen oxide output is entirely uncontrolled, so the vehicle begins the inducement sequence — warnings, then a speed limit, then a refusal to restart.
Ask whether the injector can be cleaned rather than replaced. Urea deposits dissolve in warm water, and these are not cheap parts.
Likely causes
Start here
- Crystallised reductant injector · moderate
- Frozen reductant in the tank or lines · moderate
- Blocked reductant filter · moderate
Less common
- Faulty reductant pump · moderate
- Reductant tank empty or incorrectly filled · easy
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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