P20E8 fault code: what it means

P20E8: AdBlue (DEF) pressure too low. On OM651 BlueTEC often a failed AdBlue pump; leads to a countdown to no-start.

Engine and gearbox (powertrain) · Costly if missed

Usual causes, most likely first

failed AdBlue pump (often from contaminated fluid)
low AdBlue level
blocked pick-up or air in lines

P20E8 by make

Mercedes-Benz

AdBlue (DEF) pressure too low. On OM651 BlueTEC often a failed AdBlue pump; leads to a countdown to no-start.

Usual causes: failed AdBlue pump (often from contaminated fluid); low AdBlue level; blocked pick-up or air in lines

What the repair usually costs

Crankshaft or camshaft position sensor replaceNZ$100–NZ$590 · A$100–A$580
AdBlue heater / pump / sender assembly replacementNZ$930–NZ$2,710 · A$850–A$2,400

Not sure what P20E8 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.