OBD-II · Engine and powertrain (P)
P20E8
AdBlue (reductant) pressure too low
What it means
The AdBlue pump cannot build the pressure needed to spray AdBlue into the exhaust. On vehicles with SCR, a confirmed unresolved fault may trigger reduced performance or a no-restart countdown; follow the displayed warning and the vehicle handbook.
Symptoms
- AdBlue/emissions warning, possibly with a no-start countdown
- engine warning light
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | failed AdBlue pump or tank module (very common on some makes) |
| 02 | AdBlue level very low |
| 03 | blocked filter in the tank module |
| 04 | crystallised or frozen AdBlue line or heater fault |
| 05 | leaking line or dosing injector connection |
| 06 | pump wiring or power supply fault |
What to check, step by step
- 01Check the AdBlue level and fill if low.
- 02Look for white crystals around the tank, lines and dosing injector (signs of leaks).
- 03Read live AdBlue pressure and run the pump test with a diagnostic tool.
- 04Check the pump fuse, power and ground.
- 05Replace the pump/filter or the tank module as needed; some makers only sell it as a complete tank.