P2291 – Injector control pressure, engine cranking – pressure too low

Avatar photo
By Reinier (Contact Me)
Last Updated 2024-06-08
Automobile Repair Shop Owner
CodeFault LocationProbable Cause
P2291 Injector control pressure, engine cranking - pressure too low
(Buy Part On Amazon)
Fuel pressure regulator, injector control pressure sensor

We recommend Torque Pro

Table of Contents

  1. What Does Code P2291 Mean?
  2. Where is the P2291 sensor located?
  3. What are the common causes of code P2291?
  4. How expensive is it to fix code P2291?
  5. What are the symptoms of code P2291?
  6. What are common solutions to code P2291?
  7. How serious is code P2291?
  8. How difficult is it to repair code P2291?
  9. Get Help with P2291

What Does Code P2291 Mean?

SPECIAL NOTES: Some injector control systems on Powerstroke engines use pressurized engine oil to open the injectors, but on 6.7L Powerstroke engines built between 2011 and 2016, the injectors are controlled by a high-pressure injection pump that delivers highly pressurized fuel to the injectors. Note that while the piezoelectric injectors require only about 5 000 PSI to open, the high-pressure fuel pump can generate fuel pressures of up to 26 000 PSI.

Note, therefore, that to avoid confusion, this article will focus on trouble code P2291 as it applies to 6.7L Powerstroke engines built between 2011 and 2016. END OF SPECIAL NOTES:

OBD II fault code is a generic trouble code that is defined by carmaker Ford as P2291 – “Injector control pressure, engine cranking – pressure too low” and is set when the PCM (Powertrain Control Module) detects an insufficient pressure in the high-pressure fuel system to open the fuel injectors.

All Ford Powerstroke engines have what amounts to two separate fuel systems: a low-pressure system that supplies the high-pressure injection pump with a constant supply of fuel and a high-pressure system that supplies the fuel injectors with a constant supply of pressurized fuel. Below is a generic description of the-

Low-pressure fuel system

The low-pressure fuel system uses an electric pump to extract fuel from the fuel tank. This fuel first passes through a pressure sensor that must register a fuel pressure value of at least 52 PSI before it will open to allow fuel to flow through a water separator and one or more fuel filters before it reaches the high-pressure fuel pump.

If the low-pressure fuel system fails to build a pressure of at least 52 PSI for any reason, the PCM will display a “Low Fuel Pressure” warning message on the dashboard. Moreover, if the low-pressure fuel system fails to build a pressure of at least 52 PSI, the high-pressure injection pump is starved of fuel, and the engine will crank but not start. As a practical matter, the low-pressure fuel system is calibrated to work in a range of pressures from 52 PSI to about 73 PSI, which brings us to the-

High-pressure fuel system

The high-pressure fuel pump is driven by the engine, and its timing correlates with the engine’s timing. So, provided the low-pressure fuel system can supply sufficient pressure and flow, the high-pressure injection pump delivers pressurized fuel to common rails that use fuel pressure regulators to control the fuel pressure in the fuel rail(s).

It is worth noting that the CP4.2 high-pressure pumps on 6.7L Powerstroke engines are not as robust as the upgraded CP3 high-pressure pumps. For example, reduced fuel supply, running out of fuel, or using poor quality/contaminated fuel will often cause catastrophic failure of a CP4 pump as a result of metal shards and wear particles destroying internal pump components. Note that failed CP4 pumps can typically not be repaired, meaning that the pump must be replaced with a new unit. Also, be aware that if a high-pressure fuel injection on a 6.7L fails, it is almost certain that one or more fuel injectors will be damaged as a result of the pump failure.

Having said the above, it is important to remember that insufficient pressure to control the fuel injectors can have many possible causes* apart from a failed high-pressure injection pump. Nonetheless, regardless of the root cause of the low fuel pressure issue, if the PCM detects a low fuel pressure condition in which the desired fuel pressure does not agree with the actual fuel pressure at all engine speeds and loads, it will set code P2291 and illuminate a warning light. In most instances of code P2291, the PCM will also initiate a fail-safe or limp mode that will persist until the fault is corrected.

* See the section on Possible Causes” for more details.

Where is the P2291 sensor located?

This image shows the layout of the high-pressure fuel system on a 6.7L Powerstroke engine. The high-pressure fuel pump is at the bottom center, with the injectors connected to a fuel rail for each bank of cylinders to either side of the pump. Note that, since the pump is located in the valley between the two cylinder banks, it is difficult to gain access to the pump. Therefore, we do not recommend that novice non-professional mechanics attempt to remove or install a high-pressure fuel pump on a 6.7L Powerstroke engine due to the high likelihood of damage occurring to critical injection equipment.

What are the common causes of code P2291?

Possible causes of code P2291 on 6.7L engines are many and varied, but the most common causes could include one or more of the following-

  • Failed or defective high-pressure fuel pump
  • Failed, defective, or malfunctioning pressure switch in the low-pressure fuel system
  • Failed or malfunctioning high-pressure fuel pressure regulator
  • Blocked or restricted fuel filters
  • Blocked, restricted, or damaged water separator(s)
  • Fuel pressure escaping from the injectors. Note that some pressure must escape from the injectors for the injectors to work, with the recommended flow rate in the injectors’ return line being 3ml in 15 seconds per injector.
  • Insufficient injector backpressure. The minimum allowable back pressure on each injector is 43.5 PSI. This pressure is both determined and maintained by a small orifice in the return line(s), so if this restriction fails, the required back pressure the fuel injectors require to work cannot be met or maintained

NOTE: It is important to investigate all possible causes of code P2291 before a high-pressure fuel pump is condemned out of hand. These pumps are hugely expensive, and replacing a high-pressure fuel pump unnecessarily could double or even triple the costs of resolving code P2291. Based on this, we strongly recommend that you seek professional assistance with diagnosing and resolving code P2291 if you suspect that you may have a defective high-pressure fuel pump.

How expensive is it to fix code P2291?

Due to the high number of possible causes of code P2291 on 6.7L Powerstroke engines, it is not possible to provide repair cost estimates here that will be even halfway accurate.

Nonetheless, considering that a CP4 high-pressure fuel pump can cost as much as $1000 or more, depending on the vendor, removing and installing a replacement pump usually takes between six and eight hours of labor. Moreover, if all the injectors are replaced at the same time, the repair bill could easily run into several thousand dollars.

The best way to avoid a repair bill that is higher than you are willing or able to pay is to consult several repair shops that have proven experience in diagnosing and repairing Powerstroke fuel systems. These kinds of issues are always expensive to repair, but getting several price estimates before you commit to the repair enables you to make informed decisions not only about which service provider to use but also to specify the quality of the parts that must be replaced.

Sourcing cheap parts online might save you some money now, but it’s worth keeping in mind that there are no guarantees that cheap parts will work as expected- if they work at all.

What are the symptoms of code P2291?

The most common symptoms of code P2291 are similar across all 6.7L Power stroke engines, and typically include the symptoms listed here-

  • Stored trouble code and an illuminated warning light
  • Depending on the nature of the problem, many additional trouble codes may be present along with P2291. Note that if code P2291 is not listed first on a Ford-specific scan tool, resolving the codes that precede P2291 first will usually, but not always, resolve code P2291 as well
  • The engine cranks normally but does not start
  • If the engine does start after extended cranking, it will run poorly and emit excessive clouds of black or white smoke from the tailpipe
  • The vehicle may be locked into a fail-safe or limp mode that will persist until the fault is corrected

What are common solutions to code P2291?

Some possible solutions to resolve code P2291 could include one or more of the following, but note that you will need access to Ford-specific diagnostic equipment to test the fuel return flow rate at each injector-

  • Measure the actual fuel pressure in the rails with either a capable scan tool or a suitable pressure gauge during cranking or idling. The fuel pressure in the fuel rails must be at least 5000 PSI to open the injectors
  • If the fuel pressure in the fuel rails is below 5000 PSI, check the low-pressure fuel system. This includes verifying that the low-pressure system delivers at least 52 PSI of pressure downstream of the low-fuel pressure switch, checking that fuel filters are not clogged or restricted and that the fuel is not contaminated with water or solid particulate matter such as rust or dirt
  • If the low-pressure fuel system is OK, use suitable containers to measure how much fuel leaks from each injector. The maximum allowable leak rate is 3ml per 15 seconds for each injector. Note that injectors that allow more than 3ml of fuel per 15 seconds to leak into the return line(s) are almost certainly severely damaged, and must be replaced
  • If the injectors’ leak rate and backpressure are within specs, it would be reasonable to assume that the high-pressure fuel pump has failed. However, diagnosing a high-pressure fuel pump requires specialized equipment and technical knowledge of the overall fuel system that non-professional mechanics generally do not possess
  • If the fault persists even though all other possible causes have been investigated and resolved, we strongly recommend that you seek professional assistance to resolve the problem

Note that as stated elsewhere, we do not recommend that novice non-professional mechanics attempt to remove or install a high-pressure fuel pump on a 6.7L Powerstroke engine due to the high likelihood of damage occurring to critical injection equipment.

How serious is code P2291?

In most cases, there is no advance warning that the fuel delivery system is about to fail, meaning that code P2291 and its symptoms only appear after the fuel system fails. In addition, in many instances of code P2291, the PCM derates the engine power until the engine is shut down, or dies as a result of the fuel system failure.

As a practical matter, then, and if the vehicle is still drivable, the fault must be corrected as soon as possible to prevent further damage from occurring to the high-pressure fuel pump and injectors. Therefore, code P2291 should be considered serious to critical.

How difficult is it to repair code P2291?

It is possible even for novice non-professional mechanics to perform some basic diagnostics like checking/replacing fuel filters or draining water from water separators. However, further testing and diagnostics should ideally be left to professional mechanics who have access to proper test equipment and OEM service information.

Possessing a high level of technical knowledge about the operation of fuel systems on Powerstroke engines in general and 6.7L Powerstroke engines, in particular, is a prerequisite to diagnose and repair fuel systems on Powerstroke engines, which means that the wiser option is to seek professional assistance when you are dealing with a suspected fuel delivery system failure.

Help Us Help You

Please comment below describing your issue as well as the specifics of your vehicle (make, model, year, miles, and engine). To get a detailed, expedited response from a mechanic, please make a $9.99 donation via the payment button below.