P20E8: Reductant (AdBlue) pressure too low
The AdBlue pump cannot build the pressure needed to inject the fluid into the exhaust. Usually a low level, the pump filter, a leak or the pump.
| Code | P20E8 |
|---|---|
| System | Engine and transmission |
| Group | P20xx, Emissions: catalysts and AdBlue |
| Type | Generic: it means the same on every make |
| Can you keep driving? | With care |
What P20E8 means
To spray AdBlue properly into the exhaust, the pump has to hold a set pressure in the line to the injector. The ECU has measured that this pressure stays below what it needs, so it cannot dose correctly and nitrogen oxides are not reduced as they should be.
Most common causes
- AdBlue level very low or tank empty
- Blocked AdBlue pump filter
- Leak or broken line between pump and injector
- AdBlue frozen in very cold weather, before the heater takes effect
- Worn or faulty AdBlue pump
- AdBlue pressure sensor reading wrongly
Symptoms
- Engine warning light on
- AdBlue warning on the dashboard
- Possible countdown before the engine is prevented from starting
- Ammonia smell or white marks if there is a leak
Can you drive with P20E8?
With care You can drive, but sort it out soon. On many cars, if the fault persists, a dashboard message counts down the distance left before the engine will not restart.
Open the bonnetthe in-depth explanation
How to check it
Check the AdBlue level and look under the car for white marks or crystals on the lines, which suggest a leak. If it happened during a hard frost, see whether the warning clears after a longer drive.
How to read and clear P20E8 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P20E8 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P20E4 Exhaust temperature sensors 2 and 3 on bank 1 do not agree
- P20E5 Exhaust temperature sensors 1 and 2 on bank 2 do not agree
- P20E6 The AdBlue injection air pressure is below normal
- P20E7 The AdBlue injection air pressure is above normal
- P20E9 The AdBlue pressure is above normal
- P20EA The relay supplying the reductant control unit performs incorrectly
- P20EB The relay supplying the reductant control unit performs incorrectly
- P20EC The SCR NOx catalytic converter (bank 1) is getting too hot
- P2002 Diesel particulate filter efficiency below threshold (bank 1)
- P2003 Diesel particulate filter efficiency below threshold (bank 2)
- P2004 Intake manifold runner control stuck open (bank 1)
- P2005 Intake manifold runner control stuck open (bank 2)
To understand it properly
We explain how that system works, with drawings and no waffle, in our mechanics guide: AdBlue.
What does code P20E8 mean?
To spray AdBlue properly into the exhaust, the pump has to hold a set pressure in the line to the injector. The ECU has measured that this pressure stays below what it needs, so it cannot dose correctly and nitrogen oxides are not reduced as they should be.
Can you drive with P20E8?
You can drive, but sort it out soon. On many cars, if the fault persists, a dashboard message counts down the distance left before the engine will not restart.
How do you clear P20E8?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P20E8 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
