HomeTrouble CodesP2291

P2291 — Injector Control Pressure Too Low Engine Cranking

Manufacturer-specificPowertrain (engine & transmission)

This diagnostic trouble code indicates the engine control module detected insufficient injection control pressure during engine cranking. It occurs in diesel engines utilizing hydraulic electronic unit injectors that rely on high-pressure oil to fire. The system fails to reach the minimum pressure threshold required to initiate combustion.

Symptoms

What causes it — most likely first

1. Low engine oil level or incorrect viscosity

Insufficient oil volume or oil that is too thick prevents the pump from building required pressure.

2. High-pressure oil system leaks

Worn o-rings, standpipes, or cracked fittings allow pressure to escape before reaching the injectors.

3. Malfunctioning injection pressure regulator valve

The valve controlling oil flow sticks open or fails to regulate pressure correctly during startup.

4. Worn high-pressure oil pump components

Internal wear within the pump reduces its ability to generate adequate pressure during cranking.

5. Faulty injection control pressure sensor

The sensor reports incorrect low pressure data despite adequate actual pressure in the system.

6. Engine control module internal fault

Internal computer fault preventing proper control of the pressure system, though this is rare.

How it's diagnosed

  1. Verify engine oil level and condition meet manufacturer specifications
  2. Monitor injection control pressure data via scan tool during cranking
  3. Perform high-pressure oil system air leak test
  4. Inspect injection pressure regulator valve and electrical circuit
  5. Compare sensor readings against a mechanical pressure gauge
  6. Check wiring harness continuity and control module connections

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationManufacturer-specific (P1/B1/C1/U1)

Frequently asked

Can low oil level cause this code?

Yes, insufficient oil volume prevents the pump from building required pressure.

Is replacing the computer the correct fix for this code?

No, this code is almost always caused by mechanical oil pressure issues or sensor faults, not computer failure.

Does cold weather affect this code?

Yes, thick oil in low temperatures can delay pressure buildup and trigger this code during cranking.

Will the engine run if this code is present?

Typically no, as the injectors cannot fire without adequate high-pressure oil.