Injector Ctrl Press Too Low
The PCM has detected an abnormal reading from the injector control pressure sensor (switch) or circuit. If this code is present, the driver should shut the engine off IMMEDIATELY! Catastrophic engine failure could result if this condition is not rectified at once. This type of code is limited exclusively to diesel powered applications. If this code is exhibited in your gas, hybrid, or electric vehicle suspect a defective PCM.
Code Set Parameters
The PCM monitors injector control pressure (high pressure oil) on some late model diesel vehicles, anytime the engine is running. Variations in injection control pressure that exceed a predetermined maximum, or fall below a minimum pound-per-square-inches of pressure, will cause a trouble code to be stored and a service engine soon lamp may be illuminated. Most models will illuminate the service engine soon lamp on the initial failure.
The service engine soon lamp may be illuminated and a code will be stored in the PCM. Failure to turn the engine off during a low injector pressure situation could lead to catastrophic engine failure.
Technicians report that the most common cause of this code comes from lack of oil pressure caused by lack of proper maintenance or a low oil level. Other causes include a faulty injector control pressure sensor, a defective high pressure oil injector control regulator, shorted or open wiring in the injector pressure control sensor circuit, and injector pressure control connector failure due to heat and/or corrosion.
Injector control pressure sensor replacement is common but not automatic. Many times an injector control pressure sensor is replaced to correct a low oil pressure condition that has been prolonged too long. If internal high pressure oil pump or engine failure has occurred, due to a low oil level/oil pressure condition, an injector control pressure sensor will appear to rectify the situation for a time but the low injector control pressure condition may return when the engine reaches normal operating temperature.
- Many modern diesel engines utilize an injector driver module (in conjunction with the PCM) to necessitate fuel and oil delivery to the injectors for each individual cylinder of the engine
- A high pressure oil pump and a low pressure fuel pump combine to deliver a precise measure of fuel directly to each individual cylinder
- The high pressure injection oil pump is typically driven by the camshaft and delivers high pressure oil to each individual injector via a system of steel lines or passages
- A pressure regulator is commonly used to provide consistent oil pressure to the injection system regardless of the RPM level or engine load
- The injector control pressure sensor is used to monitor oil pressure in this critical system
- Without the injection pump, efficient fuel delivery is impossible and the injectors could quickly be damaged and result in catastrophic engine failure
The injector control pressure sending unit is typically a pressure to contact switch which is threaded into a tube or passage of the high pressure oil injection system
- A low voltage (normally 5-volts) signal is supplied to the injector control pressure sensor
- This low voltage signal is grounded through the sensor
- As injector control pressure increases in the system, the sensor resistance decreases allowing the voltage input signal to the PCM to increase
- The PCM is programmed to verify a minimum and maximum voltage reading from the injector control pressure sensor in order to constantly monitor injector control oil pressure.
Several tools will be instrumental in successfully diagnosing this code
- A suitable OBD-II scanner (or code reader), a digital volt/ohmmeter, and a manual oil pressure gauge will be most helpful in performing a successful diagnosis
Begin with a visual inspection of all wiring and connectors
- Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
- Always retest the system after repairs are completed to ensure success.
If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
- This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
- Continue by clearing the code and operating the vehicle to see if it returns
- This will help to determine whether or not the malfunction is intermittent
- Make sure that the engine is filled to the proper level with suitable engine oil.
After the codes are cleared, test drive the vehicle to see if the code returns
- If the code fails to immediately return, you may have an intermittent condition
- Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made
If injector control pressure appears excessive, suspect a faulty injector control pressure sensor or injector control pressure regulator
- Replace the defective components as required, clear the codes, and operate the engine to normal operating temperature to ensure that the repair has been completed successfully.
To diagnose the low injector control pressure condition, connect the scanner or code reader and make a note of all stored trouble codes and applicable freeze frame data
- Clear the codes and shut the engine off
- Connect the manual oil pressure gauge to the injector control passage
- Start the engine and check for leaks Allow the engine to reach normal operating temperature and make a note of the actual injector control pressure reading at idle, 1,200 RPMS, and 2,500 RPMs
- Compare your findings with the manufacturer’s specifications and make engine repairs as necessary
- Clear the codes and operate the engine to normal operating temperature and beyond to make sure that your repair was successful.
If the injector control pressure is within acceptable specifications, disconnect the injector control pressure sensor connector and perform a resistance test on the sensor
- Compare your findings with manufacturer’s specifications and replace the injector control pressure sensor as needed
- If the electrical connector face of the injector control pressure sensor is contaminated with engine oil, suspect a faulty sensor (it is leaking and should be replaced).
If the sensor is within acceptable specifications, disconnect the PCM connector and perform a continuity/resistance test on all wiring circuits
- Compare your findings with manufacturer’s specifications and repair open or shorted wiring as necessary
- PCM failure is rare as a cause of this condition and PCM replacement will require reprogramming