P20F6: Reductant Injection Valve Stuck Open Bank 1 Unit 1
What to do
Get this repaired promptly rather than waiting. The injector is stuck open and fluid is going into the exhaust continuously — and undosed reductant crystallises into solid deposits inside the pipe and on the catalyst, which turns an injector repair into a much larger one.
Mention any sharp, acrid or ammonia-like smell from the exhaust. That fits this fault and helps confirm it.
Expect reductant consumption to have risen noticeably, and say so if it has.
Ask for the exhaust and catalyst face to be inspected for crystalline deposits, not just the injector replaced. Leaving deposits behind gives the new injector the same blocked path to spray into.
What this code means
The reductant injector is stuck open and delivering fluid continuously.
Stuck open is the less common half of the injector pair and the more destructive one, because unlike a blockage it keeps putting fluid where it should not be.
The mechanism is usually the same crystallisation that causes the stuck-closed fault, arriving at the opposite outcome. Deposits build on the needle and seat; instead of jamming the needle down, they hold it off. A worn or damaged seat does the same.
Continuous dosing causes harm in three distinct ways, which is why this is not merely wasteful.
- Over-dosing produces ammonia slip — unreacted ammonia passing through the catalyst, which is itself a pollutant and produces a sharp acrid smell from the exhaust.
- Undosed fluid entering a cool exhaust does not vaporise. It crystallises into solid deposits inside the pipe and on the catalyst face, restricting flow and eventually blocking it.
- Consumption rises sharply, which is what the bookkeeping check notices.
So this code frequently arrives with a consumption-too-high code, and they are one fault rather than two.
The deposits are the reason to act quickly. A blocked catalyst face is a much larger repair than an injector, and the deposits accumulate for as long as the injector keeps passing.
Ask for the exhaust to be inspected for crystalline build-up as well as the injector replaced, because leaving that behind gives the new injector the same restricted path.
Likely causes
Start here
- Crystallised reductant injector · moderate
- Faulty reductant injector · moderate
Less common
- Wiring shorted to voltage · moderate
- Reductant diluted or incorrect fluid · moderate
Rare
- Failed control module output driver · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
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
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P20F6.