474C

What Code 474C Means

Code 474C is a BMW-specific fault code that flags a plausibility error in the AdBlue (SCR) system. The engine management (DME) compares measured values (pressure, temperature, fluid level) against expected values and sets this fault when they don't match.

The AdBlue (SCR) system cuts nitrogen oxide (NOx) emissions by injecting an aqueous urea solution into the exhaust tract. Dosing has to be precise; a plausibility error means the actual parameters (circuit pressure, temperature, level, for example) don't match the calculated ones. A faulty injector, pump, or sensor can cause it, and so can urea crystallization that throws off dosing consistency.

Symptoms

• Check Engine light: the MIL illuminates or a fault message is logged.
• Countdown to no-start: the system warns that engine start will soon be locked out.
• Incorrect fluid warning: a message about wrong AdBlue quality or level.
• Reduced performance: the engine drops into limited-power mode.

Diagnosis and Repair

1. Read the codes with ISTA/D to identify the specific cause of the plausibility error.
2. Inspect the AdBlue injector for crystallization; clean or replace it as needed.
3. Verify AdBlue quality and level, then confirm the NOx sensors read accurately.
4. Reset the adaptations after the repair.

Secondary Problems

If you ignore the fault, the system can drop into limp mode and eventually block a restart of the engine. Running for a long time with incorrect dosing can damage the SCR catalytic converter and the NOx sensors.