P2291: Cranking rail pressure remains below the starting monitor boundary

P2291 is injector control pressure too low during engine cranking. Ford’s diesel summary evaluates rail pressure below 14,000 kPa for twenty seconds within the listed cranking conditions. This is a starting-phase monitor, not the normal running target-versus-actual pressure comparison used by other fuel codes.

Cranking context prevents the wrong comparison

The stated pressure corresponds to 140 bar, but the important point is the monitored phase and duration. A pressure value measured after the engine starts cannot directly establish whether the cranking threshold was satisfied during the failed attempt.

The entry table includes broad fuel and coolant temperature windows and an unset inertia switch. It also contains a fuel-tank-level value of −1 L, which is not a practical instruction about usable fuel quantity. This explanation does not reinterpret that calibration-style entry as a workshop minimum.

Preserve the starting event before assuming a cause

Useful evidence connects cranking duration with rail-pressure development and the exact engine state. A brief pressure dip does not automatically reproduce a twenty-second low-pressure condition, and repeated code clearing does not establish successful pressure buildup.

The source does not distinguish a supply issue, excessive return, pump-control problem, or measurement fault. Nor does it authorize prolonged cranking beyond the vehicle’s operating guidance. It identifies insufficient cranking pressure as observed by the controller; component isolation and safe fuel-system testing require the applicable service procedure.

Source and applicability

This explanation follows Ford’s 2023–2024 diesel OBD summary. Match the vehicle’s engine and calibration before applying these monitor values; a generic code alone does not establish fitment. Ford PDF, page 60.