P21FD: Fuel Control System B Too Rich at Higher Load (Bank 1)

What does P21FD mean?

P21FD sets when the second fuel path on bank 1 is still rich at higher load although its learned correction has already taken away the permitted maximum. No manufacturer documents the code publicly. The FCA patent for port plus direct injection engines describes three separate monitors, one per injection mode, so a rich error that appears only while the port system fuels alone can be pinned on that system rather than reported as a general P0172. Possible causes are an air mass sensor reading high at large airflow, a regulator in the low-pressure circuit holding too much pressure, or port injectors that over-deliver at long opening times. Higher fuel consumption and sooty tailpipes may follow. P2192 is the system A counterpart, P21FF the bank 2 code.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine lamp on
• Increased consumption, sooty tailpipe

Common causes

• Medium Air mass sensor reading too high at large airflow
• Medium Low-pressure regulator holding too much pressure
• Low Port injectors on bank 1 over-delivering

Likelihood is a general estimate across vehicles; your make and model may differ.