P20B9 fault code: what it means

P20B9: AdBlue heater circuit open. The tank/pump heater burning out is a known Mercedes BlueTEC fault and costly to fix.

Engine and gearbox (powertrain) · Costly if missed

Usual causes, most likely first

1. burnt-out AdBlue tank/pump heater
2. blown fuse
3. wiring fault

P20B9 by make

What the repair usually costs

• AdBlue heater / pump / sender assembly replacementNZ$930–NZ$2,710 · A$850–A$2,400
• AdBlue tank assembly or SCR catalyst replacement (dealer part)NZ$3,150–NZ$8,600 · A$2,780–A$7,650

Not sure what P20B9 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.