EPA07/10/GHG14 DDEC VI/10 Electronics and Troubleshooting Manual (DDC-SVC-MAN-0084) | 81 SPN 157 (MCM) (EPA07;EPA10;GHG14) | 81.1 SPN 157/FMI 16 – EPA07 – EPA10 – GHG14

Description Fuel Rail Pressure Too Low
Monitored Parameter Injector Cylinder #1 Needle Control Valve
Typical Enabling Conditions Fuel Rail Pressure desired – Fuel Rail Pressure Actual > 200 bar
Monitor Sequence None
Execution Frequency Continuous When Enabling Conditions Met
Typical Duration Eight Seconds
Dash Lamps MIL, CEL
Engine Reaction Derate 25%
Verification Engine Idle (One Minute)

The Motor Control Module (MCM) monitors the rail pressure and when rail pressure deviation is greater than 200 bar for eight seconds, the MCM sets the code. This fault can occur due to the conditions listed below:

  • External fuel leakage between the high pressure pump and fuel injectors
  • Pressure limiting valve leakage (internal)
  • Fuel filter integrity (loose caps, plugged filters)
  • Fuel supply issues (fuel level, fuel aeration, leaking fuel lines, fuel restrictions)
  • Intermittent loss of engine speed signal
  • High pressure pump internal failure
  • Fuel injector (amplifier or needle) leakage
  • Fuel Contamination
  • Rail pressure sensor
  • Motor Control Module (MCM)


Service Tools Used in the Procedure
Tool Number Description
J-48876 Test Gauge, Primer Port, HDE
J-48704 Caps, HP Fuel Rail, HDE
DiagnosticLink 8.x

NOTE: It is important to obtain information from the customer on when the check engine lamp occurs and if there were any performance concerns or exhaust smoke.


    1. Did SPN 157/FMI 16 appear after the fuel system was repaired or fuel filter maintenance was performed?
        1. Yes; the code may be set due to air in the fuel system. Clear codes and road test to verify complaint. If code does not set, release the vehicle. If code sets, Go to step 2.


      1. No; Go to step 2.


    1. Turn the ignition ON (key ON, engine OFF).
NOTE: On EPA10 engines with MCM software 7.6 and later, fuel tank level at the time the fault triggered can be viewed in extended data #5, “Enhanced Environmental data” Fuel Tank Level.


    1. Check and record fuel level in all fuel tanks. Is fuel level blow ¼ tank (25%)?
        1. Yes; add fuel and road test vehicle. If code does not become active during road test, release the truck. If the code becomes active during the road test with over ¼ tank (or 25%) of fuel, Go to step 4.


      1. No; view fuel tank level in extended data (EPA10) or question the driver about the fuel level when the code was set. If the level was under ¼ tank (or 25%), fuel sloshing in the tank could be the cause of aerated fuel that could cause this code. If the fuel level was over ¼ tank (or 25%) when the code was set, Go to step 4.


    1. Check for fuel contamination, including Diesel Exhaust Fluid (DEF), water, gasoline, kerosene, coolant, etc. Is contamination found?
        1. Yes; refer to section “Contaminated Fluids.”


      1. No;Go to step 5.


    1. Visually inspect for external fuel leaks on the engine and on the chassis.
        1. If a leak is found, repair leak. 


      1. If no leaks are found, Go to step 6.


    1. Using DiagnosticLink 8.x, check for multiple codes.
        1. If any of the additional fault codes are active, perform the associated diagnostics first:
          • SPN 94 / FMI 15 Fuel Filter plugged
          • SPN 94 / FMI 16 Fuel Filter plugged
          • SPN 97 / FMI 15 Water in the fuel
          • SPN 157 / FMI 1 Rail Pressure too High.
          • SPN 164 / FMI (All) Rail pressure sensor faults
          • SPN 174 / FMI 0 Fuel Temperature too High
          • SPN 679 / FMI 7 PLV stuck open
          • SPN 723 / FMI (all) Cam Sensor Codes
          • SPN 636 / FMI (all) crank sensor codes
          • SPN 1077 / FMI 5, 6 or 14


      1. If only SPN 1077/7, 157/16 or 1077/31 is present, Go to step 7.
NOTE: Do not reset this counter unless the PLV is being replaced.


    1. Using DiagnosticLink 8.x, check the value of Pressure Limiting Valve (PLV) openings. With key ON, engine OFF select the Actions tab in the top tool bar. Select Fuel System, then Pressure Limiting Valve (PLV) Change or view (E2P_RPG_CTR_PLV_OPEN) under “Extended Data Record Number 5th” list. View and record the PLV open counts. Is the counter greater than 50?
        1. Yes; replace the PLV. Verify repairs. 


      1. No;Go to step 8.
NOTE: Engines not equipped with a Low Pressure Pump Outlet (LPPO) sensor should utilize J-48706 Fuel Diagnostic Gauge Set to monitor LPPO.


    1. Perform Automatic Fuel system integrity check (FSIC) routine using DiagnosticLink 8.x. With key ON, Engine OFF (KOEO) start the Automatic FSIC. The software/tool will ask to start the engine when required. Once the engine is running, the software will have the engine enter and exit several engine operating conditions. Once the engine shuts down, leave the key on for five minutes. Disconnect DDDL and open the log file. The next part of the troubleshooting will require reviewing the FSIC log file. Go to step 9.


    1. Monitor rail pressure bleed-off time. Is bleed-off time below 35 seconds?
        1. Yes; using DiagnosticLink, perform the HP Leak Test.


      1. No; Go to step 10.


    1. Is the rail pressure bleed-off time is greater than 2 minutes 30 seconds?
        1. Yes; perform the Idle Speed Balance Test to identify faulty injector.


      1. No; Go to step 11.


    1. Does Kw/Nw show/stay “ON / Enabled / True” while the engine is running during the Automatic FSIC routine?
        1. Yes; Go to step 12.


      1. No; refer to troubleshooting for SPN 723/FMI 10.


    1. Was the fuel temperature rise greater than 10 degrees?
        1. Yes; Go to step 14.


      1. No; Go to step 13.


    1. At 600 rpm, is ASL003 Fuel Compensation Pressure within range per the fuel pressure chart? 
        1. Yes; Go to step 15.


      1. No; Go to step 14.


    1. Monitor AS124 LPPO sensor (if equipped) or use manual gauge J-48706. Is the pressure in range at 600 and 1800 rpm? 
        1. Yes; Go to step 15.


      1. No; Repair cause of incorrect fuel pressure. 


    1. Monitor AS124 LPPO (if equipped) and ASL003 Fuel Compensation Pressure at all engine speeds, are pressures stable with no oscillations?
        1. Yes; Go to step 16.


      1. No; pressures are unstable WITH oscillations of more than 1.5 psi at a steady rpm, 


    1. Check the Idle Speed Balance (ISB) Values. Are there any cylinders above 70% or below -70%?
        1. Yes; Follow repair procedures in “Idle speed balance (ISB) test” and verify repairs. 


      1. No; Go to step 17.


    1. Is ASL001 Rail Pressure erratic or does it have a saw tooth pattern?


        1. Yes; Go to step 18.
      NOTE: See examples of erratic pressure showing (1) ASL001 Rail pressure and (2) AS098 Desired rail pressure.


      1. No; Go to step 19.


    1. Perform the aerated fuel test.  Was fuel aerated?
        1. Yes; repair cause of aerated fuel. 


      1. No; replace the Quantity Control Valve. 


    1. Perform Pressure Limiting valve flow test. Did the PLV flow test pass?
        1. Yes; Go to step 20.


      1. No; replace the PLV. 


    1. Inspect the Low pressure fuel system for leaks . Are leaks present?
        1. Yes; Repair as necessary. 

      Prime fuel system prior to going to next step.


      1. No; Go to step 21.


    1. Cap the rail at all six injector feed connections using J-48704 injector rail caps and crank the engine for 10 seconds. Does the ASL001 rail pressure reach AS098 desired rail pressure?
        1. Yes; Go to step 22.


      1. No; Replace high pressure pump. .


    1. With the injectors still capped after cranking engine for 10 seconds, does the rail pressure bleed down under 100 bar in less than five minutes?
        1. Yes; Replace the high pressure fuel pump.


      1. No; Go to step 23.


    1. Using DiagnosticLink 8.x, navigate to Service Routines and Fuel System Integrity Check test and select Manual FSIC. Test drive the truck to see if the code sets. Did the code become active?
        1. Yes; Go to step 24.


      1. No; replace fuel filters and release vehicle to customer.


    1. Remove the MCM 120-Pin connector. Inspect for damage including fuel, water corrosion or bent terminals. Is any damage found?
        1. Yes; repair as needed.


      1. No; Go to step 25.


    1. Install a test MCM using the extension harness and test drive the truck. Does the Code come active?
        1. Yes; Go to step 26.


      1. No; replace MCM and verify repair.


  1. Inspect chassis fuel system for restrictions or debris. Refer to OEM procedures. Is there a chassis fuel system issue?
      1. Yes; identify source of issue and repair as necessary.


    1. No; replace fuel filters and release to customer.

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