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SPN 157 - FMI 18 (Fault Code 559)

SPN157 FMI18 (Injector Metering Rail 1 Pressure - Data Valid but Below Normal Operational Range - Moderately Severe Level)
Fault Code: 559
Fuel Rail Pressure Sensor


CODES:
Fault Code: 559
PID(P), SID(S): P157
SPN: 157
FMI: 18
Lamp: AMBER
SRT:

REASON: Injector Metering Rail 1 Pressure - Data Valid but Below Normal Operational Range - Moderately Severe Level. The ECM has detected that the fuel pressure is lower than commanded pressure.

EFFECT: Possibly hard to start, low power, or engine smoke. Engine could possibly not start.

Circuit Description:
The ECM monitors rail fuel pressure and engine operating conditions and changes the flow command to maintain the proper rail fuel pressure. Changes to the flow command result in opening (or closing) of the electronic fuel control actuator to supply more (or less) fuel to the high-pressure pump.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault Codes:
The ECM has detected that the measured fuel rail pressure is below the commanded fuel rail pressure by a calibrated limit.

Action Taken When the Fault Code is Active:
The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

Shop Talk:
Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM again.

Before performing troubleshooting work, verify the vehicle's system voltage by monitoring battery voltage in the INSITE™ electronic service tool data monitor or connecting a digital volt ohm meter to the batteries. This will help identify a potential system voltage issue.

If the engine will not start and Fault Code 559 comes active during cranking, but no speed sensor fault codes exist, monitor rail pressure with INSITE™ electronic service tool. The procedures referred to in this troubleshooting tree will also have checks for engine no start conditions.

Before servicing any fuel system components, (such as fuel lines, fuel pump, injectors, etc.) which would expose the fuel system or internal engine component to potential contaminants prior to disassembly, clean the fittings, mounting hardware, and the area around the component to be removed. Dirt or contaminants can be introduced into the fuel system and engine if the surrounding areas are not cleaned, resulting in damage to the fuel system and engine.

If fuel pressure is low, check the following:
• Fuel system prime (make sure that there is fuel in the tanks and that the system is primed)
• Fuel gear pump pressure.
If fuel gear pump pressure is correct, test for system leakage:
• High pressure pump leakage
• Injector leakage
• Fuel rail pressure relief valve leakage.

If Fault Code 559 is inactive and there are no existing performance complaints, it is possible that the vehicle was run out of fuel or that the fault came active if the engine was not primed following fuel filter replacement. Clear the inactive fault code.

Fault Code 559 sets when the engine is running and measured rail fuel pressure remains at least 100 Bar [1450 psi] less than commanded pressure. Once detected, Fault Code 559 will remain active until the engine is turned off or until the measured rail fuel pressure matches the commanded rail fuel pressure. When a condition exists that causes Fault Code 559 to become active, it is typical for the fault code to become active when the engine is heavily loaded and become inactive when the engine is lightly loaded.

When Fault Code 559 occurs, the fuel system has lost its ability to maintain rail fuel pressure. Causes of this fault include:
• Fuel inlet restrictions
• Fuel filter plugging
• Fuel gear pump output low
• Fuel gear pump pressure regulator sticking or leaking
• High pressure pump capacity decay (high leakage to drain from the high pressure pump)
• Fuel rail pressure relief valve leaks to drain
• Fuel rail pressure relief valve opens at too low a pressure
• Injector fuel circuit leaks to drain
• Pressure sensor reads more than 100 bar lower than actual pressure
• Air in the fuel.

A few bubbles exiting the line during the test is expected. A foamy appearance is an indication of a leak that allows air to enter, a severe inlet restriction that causes cavitation, or a system that is not yet primed. If fuel inlet restriction is not excessive, the source of air entry could be isolated to one of the following: suction fuel lines, OEM fuel lines, suctionside fuel filter assemblies, or stand-pipe(s) in the fuel tank(s).

The fuel rail pressure sensor can be checked. When checking the fuel rail pressure sensor accuracy, make sure the highpressure fuel rail is not pressurized. The fuel pump, high-pressure fuel lines, and fuel rail contain very high-pressure fuel. Do not loosen any fittings while the engine is running. Wait at least 10 minutes after shutting down the engine before loosening any fittings in the high-pressure fuel system, to allow the pressure to decrease to a lower level. There could be a significant amount of time waiting on the rail to depressurize completely to 0. It could be necessary to manually relieve the pressure from the high pressure fuel rail.

Intermittent ECM power supply connections can cause Fault Code 559. If the engine is running with an active Fault Code 559 and Fault Codes 449, 1911, or 2311 are not present, check the ECM power supply for intermittent connections or battery issues. Fault Code 1117 can also be active if this fault condition exits.

Inactive Fault Code/Exhausted Troubleshooting Tree:
Troubleshooting inactive Fault Code 559 can be very difficult. The fault code must be active for any of the outlined procedures in which the engine is operated during the test. For engines with high counts of inactive Fault Code 559 or if the troubleshooting tree has been exhausted, operate the engine on a chassis dynamometer or a diagnostic road test to duplicate the fault code. The most common causes of intermittent Fault Code 559 that are difficult to create are leaking high-pressure connectors that only leak when the engine and the fuel are hot, intermittent fuel supply restrictions such as debris floating in the fuel tank, and a fuel pressure relief valve that opens prematurely. Check the High Pressure Connector (HPC) and connector torque and torque to specification if necessary. Operate the engine on a chassis dynamometer or conduct a diagnostic road test to duplicate the fault code. Use INSITE™ electronic service tool to log fuel system parameters during testing.

Fuel Flow

CODES:
Fault Code: 559
PID(P), SID(S): P157
SPN: 157
FMI: 18
Lamp: YELLOW
SRT:

REASON: Injector Metering Rail 1 Pressure - Data Valid But Below Normal Operating Range - Moderately Severe Level. The engine control module (ECM) has detected that fuel pressure is lower than commanded pressure.

EFFECT: Possibly hard to start or low power. Engine could possibly not start.

Circuit Description:
The pressure control loop relies on fuel pressure supplied to the high-pressure pump by the fuel gear pump. The ECM monitors rail fuel pressure and engine operating conditions and changes the flow command to maintain the proper rail fuel pressure. Changes to the flow command result in opening (or closing) of the fuel pump actuator to supply more (or less) fuel to the high-pressure pump.

Component Location:
Use the following procedure for a detailed component location view.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault Codes:
The ECM has detected the measured fuel rail pressure is below the commanded fuel rail pressure by at least 250 bar [3625 psi] for 7 seconds.

Action Taken When the Fault Code is Active:
The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

Shop Talk:
The fuel system is designed to run on clean fuel. It has two fuel filters to maintain this cleanliness. Carelessness in handling and storage of fuel system components during the repair can subject the precision components to damaging debris. Before servicing any fuel system components (such as fuel lines, fuel pump, injectors, etc.), clean the fittings, mounting hardware, and the area around the component to be removed. Store the components in a clean environment. Keep all fuel port openings and line ends covered so that no dirt can enter.

Fault Code 559 sets when the engine is running and measured rail fuel pressure remains at least 250 bar [3625 psi] less than commanded pressure. Once detected, Fault Code 559 will remain active until the engine is turned OFF or until the measured rail fuel pressure matches the commanded rail fuel pressure. When a condition exists that causes Fault Code 559 to become active, it is typical for the fault code to become active when the engine is heavily loaded and become inactive when the engine is lightly loaded.

Possible causes of this fault code include:
• Fuel inlet restrictions (filters, low pressure fuel lines, OEM plumbing, etc.)
• Sticking check valve in ECM cooling plate
• Fuel gear pump output low
• Fuel gear pump pressure regulator stuck open (this can result in hard start and/or no-start complaints)
• High-pressure pump capacity decay (high leakage to drain from the high-pressure pump)
• Fuel rail pressure relief valve leaks to drain
• Fuel rail pressure relief valve opens at a pressure too low (Fault Code 3727 detects this condition)
• Injector fuel circuit leaks to drain (injector body, high-pressure connectors, etc.)
• Air in the fuel or suction leaks at gear pump shaft seal (can result in hard start and/or no start complaints)
• Fuel level is below the suction line in the fuel tank
• Restricted fuel screen, located in the banjo bolt, at the high-pressure fuel pump inlet, if equipped
• External fuel leaks.

If Fault Code 559 is inactive and there are not any existing performance complaints, it is possible the vehicle was run out of fuel or the fault became active if the engine was not primed following fuel filter replacement. However, if the customer reports that the fault code becomes active during engine operation, the steps in this fault code diagnostic tree can be used to identify the cause and make a repair.

If the engine will not start and Fault Code 559 becomes active during cranking, and no speed sensor fault codes exist, it is most likely that the engine is not developing rail pressure during cranking. Possibly, the engine is not primed, gear pump pressure is too low, or the high-pressure fuel system components have excessive leakage to drain. The procedures referred to in this troubleshooting tree also have checks for engine no start conditions.

The steps of this fault code tree assume that the fault condition is repeatable (this does not necessarily mean that the fault code is active with the engine at idle). The troubleshooting has been designed to isolate the problem into four categories:
1. Other more precise fault codes exist (example: electrical circuits faults).
2. Isolate the high-pressure system; determine if the high-pressure system has high leakage.
3. Isolate the low pressure system; determine if the low pressure system works correctly. The system must first be primed. Then, it is important to note that checks of gear pump pressure and inlet restriction involves using a special service tool that causes the flow rate to increase to a rated flow. Fuel gear pump pressure and/or inlet restriction can not be accurately measured without a method of increasing the flow (i.e. using the special service tool or operating the engine at full power).
4. Verify the ECM calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM.

Troubleshooting inactive Fault Code 559 can be difficult. For engines with high counts of inactive Fault Code 559, or if the troubleshooting tree has been exhausted, operate the engine on a chassis dynamometer or conduct a diagnostic road test to duplicate the fault code. Be certain to have a fuel pressure gauge installed at the pressure filter outlet side during the test.

If the accuracy of the fuel rail pressure sensor is being questioned, a key ON accuracy check can be performed. When checking the fuel rail pressure sensor accuracy, make sure the high-pressure fuel rail is not pressurized. The fuel pump, high-pressure fuel lines, and fuel rail contain very high-pressure fuel. Do not loosen any fittings while the engine is running. Once the engine is keyed OFF, there could be a significant amount of time waiting for the fuel to depressurize to 0 bar [0 psi]. It is necessary to manually relieve the pressure from the high-pressure fuel rail by loosening the pump-to-rail line at the rail. At key ON, a depressurized rail pressure sensor should read 0 ± 43 bar [624 psi].



Read More:
SPN 101 - FMI 0 (Fault Code 556)
SPN 101 - FMI 16 (Fault Code 555)









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