P20F6
Injection Valve Stuck Open Bank 1 Unit 1P20F6 is a generic OBD-II powertrain diagnostic trouble code: Injection Valve Stuck Open Bank 1 Unit 1. It is logged by the engine control unit when the scr/adblue monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P20F6 means
P20F6 — Reductant Injection Valve Stuck Open Bank 1 Unit 1 — is an SAE generic code indicating that the primary AdBlue dosing injector for the SCR catalyst cannot be commanded closed by the SCR control module. Unlike P208E (stuck closed), this fault causes continuous or uncontrolled AdBlue flow into the exhaust system even when dosing is not commanded. The SCR module infers the stuck-open condition by monitoring system pressure when the injector should be sealed: if pressure drops abnormally or the dosing pump runs continuously to maintain pressure, the module concludes the injector is passing fluid when it should be closed.
A stuck-open dosing injector is the more consequential of the two injector mechanical faults. Excess urea deposition in the SCR catalyst and exhaust pipe leads to ammonium sulphate and ammonium carbamate crystal formation, which can block the catalyst substrate and damage the downstream NOx sensor. In severe cases, large urea deposits can partially obstruct exhaust flow, increasing back-pressure and stressing the turbocharger. AdBlue consumption will be abnormally high, providing an early warning sign before fault codes appear.
The fault triggers the MIL and NOx countermeasure logging. If unresolved, AdBlue overconsumption will empty the tank prematurely, itself triggering a separate low-level fault and dosing shutdown.
Common causes
Most-frequently reported root causes when P20F6 is logged.
-
1
Damaged or worn injector solenoid seat allowing fluid to bypass when de-energised
-
2
Urea crystal debris holding the injector needle off its seat
-
3
Injector solenoid coil stuck energised due to a short in the drive circuit
-
4
Contaminated AdBlue with particulates jamming the needle in the open position
-
5
Failed injector return spring allowing the needle to remain open
-
6
Damaged injector O-ring causing bypass around the needle (less common)
Symptoms drivers notice
How to diagnose P20F6
A typical diagnostic flow when this code is present.
-
1
Connect a scan tool and confirm P20F6; also check for NOx sensor fault codes or abnormal NOx sensor readings caused by urea deposit contamination of the sensor
-
2
Inspect AdBlue consumption over the last service interval — abnormally rapid depletion is a strong indicator of a stuck-open or bypassing injector
-
3
Inspect the dosing injector nozzle and surrounding exhaust area for white crystalline deposits indicating continuous urea flow
-
4
Remove the injector and bench test by applying voltage to the solenoid coil then removing it; fluid should flow when energised and stop immediately when de-energised
-
5
Inspect the injector needle and seat for debris, wear, or foreign material holding the valve open; attempt cleaning with warm distilled water
-
6
Replace the dosing injector if the needle does not seal positively when de-energised
-
7
After repair, inspect the SCR catalyst for urea crystal blockage; if catalyst backpressure is elevated, a regeneration or catalyst service may be required
Related powertrain codes
- B0001 — PCM Discrete Input Speed Signal Error
- B0004 — PCM Discrete Input Speed Signal Not Present
- C0359 — Four Wheel Drive Low Range (4LO) Discrete Output Circuit
- C0362 — 4LO Discrete Output Circuit High
- P2000 — NOx Adsorber Efficiency Below Threshold Bank 1
- P2001 — NOx Adsorber Efficiency Below Threshold Bank 2
Frequently asked questions
Is P20F6 more serious than P208E (stuck closed)?
Both are serious for different reasons. P208E means no SCR dosing and NOx exceedance. P20F6 means uncontrolled dosing that risks catalyst damage from urea crystal accumulation. P20F6 often has more collateral damage potential if left unrepaired.
Can I top up AdBlue and keep driving with P20F6?
Topping up only postpones the problem. Uncontrolled urea injection will damage the SCR catalyst and potentially the downstream NOx sensor. The injector must be repaired before continued operation.
How do I confirm the injector is stuck open versus a dosing pump that is over-pressuring?
Remove the dosing injector and observe: with the injector de-energised and system pressurised, a stuck-open injector will drip or flow continuously. A pump fault will show abnormal pressure on a pressure gauge but no flow from a closed (functional) injector.
Will the SCR catalyst recover after a stuck-open injector is fixed?
Mild urea crystal build-up can often be cleared by running high-temperature regeneration cycles after repair. Severe blockage may require catalyst replacement. Monitor exhaust backpressure differential after repair to assess catalyst condition.
Disabling P20F6 in software
RaceTune can permanently disable P20F6 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
ECUs with a P20F6 disable in our catalogue
Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.
- Bosch EDC17C60 verified 2 software versions
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
Got P20F6 in your scan?
Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.
Upload your file