P20BD fault code: what it means

P20BD: AdBlue (reductant) heater B circuit open. AdBlue can freeze or stop dosing; a no-restart countdown can follow.

Engine and gearbox (powertrain) · Costly if missed

Usual causes, most likely first

failed AdBlue tank heater
wiring or plug fault

P20BD by make

Mercedes-Benz

AdBlue (reductant) heater B circuit open. AdBlue can freeze or stop dosing; a no-restart countdown can follow.

Usual causes: failed AdBlue tank heater; wiring or plug fault

What the repair usually costs

AdBlue tank assembly or SCR catalyst replacement (dealer part)NZ$3,150–NZ$8,600 · A$2,780–A$7,650

Not sure what P20BD 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.