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.
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 this same explanation and whether it’s confirmed, pending or permanent.
With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.
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 the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.
Similar codes
- P2097 Post-catalyst fuel trim system too rich (bank 1)
- P2098 Post-catalyst fuel trim system too lean (bank 2)
- P2099 Post-catalyst fuel trim system too rich (bank 2)
- P20B9 Reductant (AdBlue) heater A control circuit open or faulty
- P20EE SCR NOx catalyst efficiency below threshold (bank 1)
- 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)
P20E8 is a generic code, so it means the same on any make, for example on Audi, BMW, Fiat, Mazda, Peugeot, Volkswagen. See what Final OBD does on your car in makes and models.
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 the faults of every control unit for free, including each make’s own codes, and with Pro explains each one in plain English. Free clears engine faults at no cost.
Coming soon
Mid to late October 2026
If you want to try it in your car before anyone else, send us your email and we will add you as a tester.
info@finalobd.com