P20F6–P20F7 Reductant Injection Valve Stuck Open Bank 1 Unit 1
The part is not moving as commanded - physically stuck rather than electrically dead.
Can you drive it? The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.
Which code is which
Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.
| Code | Definition | Severity |
|---|---|---|
P20F6 | Reductant Injection Valve Stuck Open Bank 1 Unit 1 | Investigate soon |
P20F7 | Reductant Injection Valve Stuck Open Bank 2 Unit 1 | Investigate soon |
The definition
P20F6: Reductant Injection Valve Stuck Open Bank 1 Unit 1.
P20F6 is a manufacturer-specific powertrain code (the engine or gearbox). Its meaning is set by the carmaker rather than by the SAE standard, so a generic OBD-II reader will often show it as an unknown code or misread it.
What to check first
Cheapest and fastest checks first:
- Check the part can move by hand with the engine off, where it is safe to do so.
- Look for carbon or soot build-up, which is the usual reason a flap or valve stops moving on these engines.
What actually causes this on a VAG
The reductant injection valve is the AdBlue injector: it sprays a fine mist of AdBlue into the hot exhaust ahead of the SCR catalyst, where it converts NOx into nitrogen and water. This code means the ECU believes it is leaking or not shutting, so AdBlue is passing when it should not be. Signs include unusually high AdBlue consumption, a sharp ammonia-like smell, and white crystalline deposits around the injector or the exhaust joint. Most VAG AdBlue systems use a single injector, which is what 'bank 1 unit 1' refers to; newer twin-dosing systems use two. Worth knowing before you start: VW and Audi's own fault-code list carries stuck closed for this valve but not stuck open, so on VAG equipment a leaking or over-dosing injector more usually appears as reductant consumption too high, reductant injection valve range/performance, or reductant system performance bank 1. Those are the same investigation as this one - do not treat them as separate faults chasing separate parts.
Most likely causes, in order
- Wrong or contaminated fluid in the AdBlue tank. Ask this first because it costs nothing to ask. Diesel, screenwash or ordinary water put into the AdBlue filler wrecks the whole dosing system, and a contaminated injector will not seal. Find out whether anything else has ever gone in the tank and have the fluid itself checked before any parts are ordered - it happens more often than people expect, and it turns a one-part job into a whole-system replacement.
- Crystallised AdBlue on the nozzle or seat. This is the usual actual finding. AdBlue dries into a hard white crystalline deposit that builds on the injector tip and the sealing face until the valve cannot close cleanly, and the same deposits accumulate in the mixer downstream where they start restricting the exhaust. Note that on many VAG applications the injector is coolant-cooled, so removing it to inspect means dealing with coolant hoses - it is not a two-minute job.
- Dosing system not holding pressure. The ECU infers 'stuck open' partly from how the metering pressure behaves, so a pump or dosing module that cannot hold pressure, or air in the lines after a repair or a run-dry, can produce this with a perfectly good injector. Watch commanded against actual dosing pressure and whether it bleeds away when dosing stops and the system runs its purge cycle.
- Failed injector solenoid or seat. Once the fluid and the pressure side have been checked, a genuinely worn or seized-open injector is the remaining answer. These are supplied as a sealed unit and are not repairable.
Worth knowing: Check the fluid before you buy an injector - putting anything other than proper AdBlue in the tank contaminates the pump, lines and injector together. Be aware too that on Euro 6 VAG diesels an unresolved AdBlue system fault starts a legally mandated countdown that reduces performance and eventually prevents the engine from restarting, so this is not one to leave for a few months.
Reading the code is the easy part
A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.
VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.
$249 once. No subscription, unlimited cars. Windows 10/11.
See VAGPULSE — $249 Look up another codeSoftware downloads instantly · cable ships September 30 · cable guarantee — refund if it won't connect
Prefer to work on your phone? The VAGPULSE Android app is a free download and its demo mode runs against a sample car with no hardware at all, so you can see exactly what it reads before spending anything. Reading your car with it needs the VAGPULSE cable, which comes with the licence.
Common questions
What does P20F6 mean?
P20F6 means Reductant Injection Valve Stuck Open Bank 1 Unit 1. The part is not moving as commanded - physically stuck rather than electrically dead.
Can I drive with P20F6?
The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.