A4 P0171 Kraftstoffbemessungssystem zu mager | Posts 16+

If the rail pressure is too low, the "too lean" error is likely a secondary error.

Before checking the fuel pump or fuel pressure regulator, I would first make sure that the corresponding filters are not clogged and that the fuel pump is receiving enough fuel.

Is the fuel tank vent working properly?

Best regards, Rainer.

The workshop has ordered a new high-pressure pump.
It will be installed on Monday.
Thank you for your patience with a beginner...

Solarsepp

"I also had the rail pressure error. It was easy to track down and reproduce in the log (full throttle in a high gear starting at 1000 RPM)."

Since my engine has a dual injection system, the "too lean" error likely didn't occur because the intake manifold injection took over.

They also replaced the fuel pump under warranty.