Over Pressurized DEF System
SPN 4374/FMI 1
Description Over Pressurized Diesel Exhaust Fluid (DEF) System
Monitored Parameter DEF Pump Speed vs. DEF Pressure
Typical Enabling Conditions DEF Pump Enabled OR On-Off-Cycle Request
Monitor Sequence None
Execution Frequency Continuous When Enabling Conditions Met
Typical Duration 2 Minutes
Dash Lamps MIL, CEL
Engine Reaction None
Verification ADS Self-check

Check as follows:

Show/Hide Checkboxes
1. Connect DiagnosticLink® .

2. Turn the ignition ON (key ON, engine OFF).

3. Check for multiple codes. Are any other faults active in addition to SPN 4374/FMI 1?1. Yes; Diagnose and repair the other faults first. Verify repair.
2. No; Go to step 4.

4. Verify the Aftertreatment Control Module (ACM) software level is e5.57.0.0 or newer. Compare the current ACM software level to the server. Is the ACM software at the latest level?
1. Yes; Go to step 5.
2. No; update the ACM software level and perform the verification procedure in the table above. If the fault code does not return, release the vehicle. If the fault code returns, Go to step 5.

5. Turn the ignition OFF.

6. Disconnect the DEF dosing unit electrical harness connector.

7. Inspect the DEF dosing unit electrical harness wiring and connector for signs of damage, bent, spread, corroded or unseated (pushed out) pins, moisture in the connector or wire damage near the connector. Is any damage found?
1. Yes; repair as necessary. Perform Selective Catalytic Reduction Airless Dosing System (SCR ADS) Self-Check Routine to verify repairs.
2. No; Reconnect harness connector. Go to step 8.

8. Disconnect the DEF return line from the DEF dosing unit. Refer to section “Removal of the GHG14 Diesel Exhaust Fluid Lines” . Connect a temporary drain hose from the DEF dosing unit return fitting into a DEF-safe container.

9. Clear fault codes.

10. Perform SCR ADS Self-Check Routine. Did the SCR ADS test pass with flow from dosing unit return line into the DEF-safe container?
1. Yes; Replace DEF return line. Go to step 11.
2. No; replace DEF dosing unit. Refer to section “Removal of the GHG14 Dosing System Doser” . Verify repair.

11. Reconnect all DEF lines and connectors. Perform SCR ADS Self-Check Routine to prime the system. Did the SCR ADS Self-Check Routine complete successfully?
1. Yes; release vehicle.
2. No; replace DEF dosing unit.

Under Pressurized Diesel Exhaust Fluid System

SPN 4374/FMI 0

Description This Code Sets When the Diesel Exhaust Fluid (DEF) Pump Speed is Higher than Normal For a Given DEF Pressure
Monitored Parameter DEF Pump Speed, DEF Pressure
Monitor Sequence None
Execution Frequency Continuous When Enabling Conditions Met
Typical Duration Continuous Until Resolved
Dash Lamps MIL, CEL
Engine Reaction Derate 25%
Verification SCR ADS Self-Check

Possible causes:
• Restriction in the DEF line between the DEF tank and the DEF pump
•Restriction in the DEF line between the DEF pump and the DEF dosing unit
• Air in the DEF line between the DEF tank and the DEF pump
• Restriction in the DEF pump
•Failed DEF pump

Check as follows:

Show/Hide Checkboxes

NOTICE:
Customers in colder climates where winter ambient air temperatures generally stay below -11° C (12°F) need to verify that the DEF is not frozen before troubleshooting this fault code.
1. Connect DiagnosticLink® .
2. Turn the ignition ON (key ON, engine OFF).
3. Check for multiple codes. Are codes SPN 4334/FMI 3, 4, SPN 4375/FMI 3, 4, or SPN 3361/FMI 3, 4, 5 also present?1. Yes; diagnose and repair the other fault codes first. Verify repair.
2. No; Go to step 4.

4. Turn the ignition OFF.
5. Inspect the DEF tank vent tube. Is there any blockage or restriction?1. Yes; clear the restricted vent tube. Go to step 6.
2. No; Go to step 6.

6. Using DEF test strip A0005850202, check for diesel fuel or oil contamination of the DEF fluid. Does the test strip indicate contamination?1. Yes; replace the following components and refill the system with new DEF:
◾ DEF tank
◾ DEF tank header
◾ DEF supply line from the DEF tank to the DEF pump
◾ DEF line from the DEF pump to the DEF dosing unit
◾ DEF return line from the DEF dosing unit to the DEF tank
◾ DEF pump
◾DEF dosing unit

2. No; Go to step 7.

To avoid injury from flying debris when using compressed air, wear adequate eye protection (face shield or safety goggles) and do not exceed 276 kPa (40 psi) air pressure.
7. Inspect the DEF line that runs from the DEF pump to the DEF dosing unit. Is the DEF line damaged, pinched, or kinked?1. Yes; replace the DEF line from the DEF pump to the DEF dosing unit.
2. No; Go to step 8.

8. Inspect the DEF line that runs from the DEF tank to the DEF pump. Is the DEF line damaged, pinched, or kinked?1. Yes; replace the DEF line from the DEF tank to the DEF pump.
2. No; Go to step 9.

9. Disconnect the DEF supply line at the dosing unit. Fill the graduated cylinder supplied in DEF test kit (P/N: W060589001900) with water. Place the end of the DEF line into the graduated cylinder as far as possible.

NOTE: Place the graduated cylinder in a secondary container to catch over flowing DEF fluid, making sure you still have clear sight of the end of the DEF line.
10. Using DiagnosticLink, perform the Selective Catalyst Reduction Airless Dosing System (SCR ADS) Self-Check routine. When the service routine is running, visually inspect the DEF line for continuous air bubbles coming from the line and DEF flow.
11. Were any bubbles coming from the DEF pump supply line indicating a crack in the DEF pump feed line?1. Yes; replace the DEF supply line from the DEF tank to the DEF pump. Verify repair.
2. No; Go to step 12.

12. Remove the DEF tank header.
13. Inspect inside the DEF tank for debris that may be floating around or stuck to the DEF tank header pick up screen. Was any debris found?1. Yes; flush out the DEF tank and clean the DEF tank header filter screen. Go to step 14.
2. No; Go to step 14.

NOTICE:
The RS SUPPLY KIT contains all the necessary parts for steps 14-17.14. Using the DEF/Doser Kit (RS SUPPLY KIT – available through eParts catalog), replace the DEF pump module filter. Refer to section “Installation of the GHG14 Diesel Exhaust Fluid Pump Filter” . Go to step 15.

15. Replace the DEF pump inlet screen. Refer to section “Installation of the Diesel Exhaust Fluid Pump Module Filter Screen” . Go to step 16.
16. Replace DEF Pressure Relief Valve (PRV). Refer to section “Removal of the Diesel Exhaust Fluid Pump Pressure Relief Valve” . Go to step 17.
17. Replace DEF dosing unit inlet screen. Refer to section “Removal of the GHG14 Diesel Exhaust Fluid Dosing Unit Inlet Screen” . Go to step 18.

NOTE: If air pressure is greater than 827 kPa (120 psi), use a pressure regulator.
18. Prime pump with shop air. Using a rubber tipped air gun to seal around the DEF pump inlet fitting, apply clean regulated shop air to the DEF pump inlet fitting for three to five seconds.
d140723a

19. Connect all DEF lines and electrical connections. Go to step 20.

NOTE: Performing the Selective Catalytic Reduction Airless Dosing System (SCR ADS) Self-Check Routine may fail the first couple of times until the system is fully primed.
20. Perform Selective Catalytic Reduction Airless Dosing System (SCR ADS) Self-Check Routine two times to further prime the system. Ignore the results of these two tests and Go to step 21.
21. Perform Selective Catalytic Reduction Airless Dosing System (SCR ADS) Self-Check Routine to check the operation of the system. Did the SCR ADS test pass?1. Yes; replacing the DEF Pressure Relief Valve (PRV) in the kit resolved the concern. No further diagnostics or repairs are needed.
2. No; replace the DEF pump.

DEF Inducement DEF Lamp Active

SPN 521049/FMI 31

Description This Code Sets When There is a Code Present for the Diesel Exhaust Fluid (DEF) Tank Level, DEF Dosing Unit, DEF Pump, NOx Sensors, Blocked DEF Line, DEF Quality, NOx Efficiency, Selective Catalyst Reduction (SCR) Harness and/or SCR Sensor.
Monitored Parameter SCR and Diesel Particulate Filter (DPF) Sensors
Typical Enabling Conditions Always Enabled
Monitor Sequence None
Execution Frequency Always Enabled
Typical Duration Two Seconds
Dash Lamps DEF Lamp
Engine Reaction 25% Derate
Verification High Idle Regeneration followed by a Parked SCR Efficiency Test

Check as follows:

Show/Hide Checkboxes
1. Connect DiagnosticLink®

2. Turn the ignition ON (key ON, engine OFF).

During parked regeneration the exhaust gases will be extremely HOT and could cause a fire if directed at combustible materials. The vehicle must be parked outside.

3. Check for other emission-related fault codes. Are there any Selective Catalyst Reduction (SCR) or Diesel Particulate Filter (DPF) related fault codes present?1. Yes; diagnose and repair the emission-related fault codes first. Verify repair.

2. No; perform a high idle regeneration. When the engine returns to idle, turn the ignition OFF and wait for all the modules to power down (usually about one minute). Turn the ignition ON (key ON, engine OFF) and wait one minute, then start the engine and run a Parked SCR efficiency test. Use DiagnosticLink to clear the code.

Soot Level Very High

NOTE: Do not interrupt regeneration once it has been initiated.

NOTE: When this code is detected, the operator has two minutes to execute the entry conditions, cycle clutch switch (manual transmission), cycle parking brake, cycle neutral switch (automatic transmission), then initiate regeneration request. If this procedure is not completed within this time limit, the engine will shut down and the regeneration procedure must be restarted.

During parked regeneration the exhaust gases will be extremely HOT and could cause a fire if directed at combustible materials. The vehicle must be parked outside.

1. Perform a parked regeneration.
2. Clear all codes following the completion of the parked regeneration.

1. Check for multiple codes.
   1. If SPN 3609/FMI 4 and SPN 3610/FMI 4 are present, repair open between Aftertreatment Control Module (ACM) pin 117 and Diesel Oxidation Catalyst (DOC)/Diesel Particulate Filter (DPF) pressure sensors pin 3.
   1. If only SPN 3609/FMI 4 is presentGo to step 2.

1. Turn the ignition OFF (key OFF, engine OFF).

1. Disconnect the DOC inlet pressure sensor.

1. Inspect the DOC inlet pressure sensor harness for bent, spread, or corroded pins.
   1. If the pins are bent, spread, or corroded, repair as necessary.
   1. If the connector shows no signs of damage,Go to step 5.

1. Disconnect the ACM 120-pin connector.

1. Measure the resistance between pin 2 of the DOC inlet pressure sensor and ground.
   1. If the resistance is less than 1k ohms, repair short to ground between pin 2 of the DOC inlet pressure sensor and pin 87 of the ACM 120-pin connector.
   1. If the resistance is greater than 1K ohmsGo to step 7.

1. Measure the resistance between pin 2 of the DOC inlet pressure sensor and pin 87 of the ACM 120-pin connector.
   1. If the resistance is greater than 3 ohms repair wire between pin 2 of the DOC inlet pressure sensor and pin 87 of the ACM 120-pin connector.
   1. If the resistance is less than 3 ohms, replace the DOC inlet pressure sensor

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

• Faulty fuel rail pressure sensor
• Faulty Quantity Control Valve (QCV)
• Faulty MCM
• Faulty Wiring

1. Turn the ignition ON (key ON, engine OFF).

1. Using DiagnosticLink^® , check for multiple codes. Are additional codes, excluding ACM codes, present along with SPN 157/FMI 18?
   1. Yes; troubleshoot the additional codes first.
   1. No; Go to step 3.

1. Check actual fuel rail pressure (key ON, engine OFF). Is actual fuel rail pressure greater than 5 bar?
   1. Yes; Go to step 4.
   1. No; Go to step 5.

1. Remove the fuel rail pressure sensor and reconnect the sensor to the harness.  Is the fuel rail pressure sensor reading greater than 5 bar with sensor removed from rail?
   1. Yes; replace the fuel rail pressure sensor. 
   1. No; install the removed fuel rail pressure sensor. Go to step 5.

1. Perform the Fuel System Integrity Check (FSIC) test using DiagnosticLink^® .

1. Is the actual fuel rail pressure (ASL001) 200 bar higher than the desired rail pressure (AS098) at any point during the FSIC test?
   1. Yes; replace the quantity control valve.
   1. No; the deviation is less than 200 bar, Go to step 7.

1. Inspect the fuel rail pressure sensor connector and MCM 120-pin connector for corrosion, bent, spread, or damaged pins. Is any damage found?
   1. Yes; replace the damaged component.
   1. No; replace the fuel rail pressure sensor. 

EPA07/10/GHG14 DDEC VI/10 Electronics and Troubleshooting Manual (DDC-SVC-MAN-0084) | 90 SPN 164 (MCM) (EPA10;GHG14) | 90.6 SPN 164/FMI 21 – EPA10 – GHG14

Check as follows:

1. Disconnect the fuel rail pressure sensor.

1. Inspect the fuel rail pressure sensor connector and harness connector for signs of damage: bent, spread, broken, unseated (pushed out) or corroded pins, signs of water intrusion or damaged wiring near the connector.
   1. If signs of damage are present, repair as necessary.
   1. If no signs of damage are present, Go to step 3.

1. Turn the ignition ON (key ON, engine OFF).

1. Measure the voltage between pins 1 and 3 of the fuel rail pressure sensor harness connector.
   1. If the voltage is between 4.5 and 5.5 volts, Go to step 6.
   1. If the voltage is not between 4.5 and 5.5 volts, Go to step 5.

1. Measure the voltage between pin 3 of the fuel rail pressure sensor harness connector and battery ground.
   1. If the voltage is between 4.5 and 5.5 volts, repair the wire between pin 1 of the fuel rail pressure sensor harness connector and pin 102 of the MCM 120-pin connector.
   1. If the voltage is not between 4.5 and 5.5 volts, repair the wire between pin 3 of the fuel rail pressure sensor and pin 58 of the MCM 120-pin connector.

1. Turn the ignition OFF.

1. Disconnect the MCM 120-pin connector.

1. Inspect the MCM 120-pin connector and harness connector for signs of damage; bent, spread, broken, unseated (pushed out) or corroded pins, signs of water intrusion or damaged wiring near the connector.
   1. If signs of damage are present, repair as necessary.
   1. If no signs of damage are present, Go to step 9.

1. Measure the resistance between pin 2 of the fuel rail pressure sensor harness connector and pin 78 of the MCM 120-pin connector.
   1. If the resistance is less than 5 ohms, Go to step 10.
   1. If the resistance is greater than 5 ohms, repair the wire between pin 2 of the fuel rail pressure sensor harness connector and pin 78 of the MCM 120-pin connector.

1. Measure the resistance between pin 3 of the fuel rail pressure sensor harness connector and pin 58 of the MCM 120-pin connector.
   1. If the resistance is less than 5 ohms, Go to step 11.
   1. If the resistance is greater than 5 ohms, repair the wire between pin 3 of the fuel rail pressure sensor harness connector and pin 58 of the MCM 120-pin connector.

1. Measure the resistance between pins 1 and 2 of the fuel rail pressure sensor harness connector.
   1. If the resistance is greater than 10K ohms, Go to step 12.
   1. If the resistance is less than 10K ohms, repair the short in the wires between pins 1 and 2 of the fuel rail pressure sensor harness connector.

1. Reconnect the MCM 120-pin harness connector.

1. Turn the ignition ON (key ON, engine OFF).

1. Measure the voltage between pins 1 and 3 of the fuel rail pressure sensor harness connector.
   1. If the voltage is between 4.5 and 5.5 volts, replace fuel rail pressure sensor. 
   1. If the voltage is not between 4.5 and 5.5 volts, repeat the above procedure. If the results are the same, replace the MCM module. 

1. Connect DiagnosticLink^® . Go to step 2.

1. Turn the ignition ON (Key ON, Engine OFF). Go to step 3.

1. Check for multiple codes. Are codes SPN 4335/FMI 3 or SPN 3510/FMI 3 also present?
   1. Yes; Go to step 4.
   1. No; Go to step 9.

1. Turn the ignition OFF. Go to step 5.

1. Disconnect the DEF air pressure sensor electrical connector. Go to step 6.

1. Turn the ignition ON (Key ON, Engine OFF). Go to step 7.

1. Measure the voltage between pin 3 of the DEF pressure sensor connector, harness side and ground. Is the voltage greater than 5 volts?
   1. Yes; repair the short to power on pin 84 of the 120-pin ACM connector. Verify repair.
   1. No; Go to step 8.

1. Measure the voltage between pin 3 of the DEF pressure sensor connector, harness side and ground. Is the voltage between 4.5 and 5 volts?
   1. Yes; repair the open circuit between pin 2 of the DEF pressure sensor and pin 99 of the 120-pin ACM connector.
   1. No; repair the open circuit between pin 3 of the DEF pressure sensor and pin 84 of the 120-pin ACM connector. Verify repair.

1. Turn the ignition OFF. Go to step 10.

1. Disconnect the DEF pressure sensor. Measure the voltage between pin 3 of the DEF pressure sensor connector, harness side and ground. Is the voltage between 4.5 and 5 volts?
   1. Yes; Go to step 11.
   1. No; repair the open between pin 3 of the DEF pressure sensor connector and the circuit splice. Verify repair.

1. Measure the voltage between pin 2 of the DEF pressure sensor connector, harness side and pin 3 of the DEF pressure sensor connector, harness side. Is the voltage between 4.5 and 5.0 volts?
   1. Yes; replace the DEF pressure sensor. Verify repair.
   1. No; repair the open between pin 2 of the DEF pressure sensor connector and the circuit splice. Verify repair.

1. Are any cooling system issues present?
   1. Yes; repair cooling system issues first.
   1. No; Go to step 2.

1. Check for other fault codes. Is fault code SPN 110/FMI Any or SPN 4193/FMI Any also present?
   1. Yes; diagnose other fault code first.
   1. No; Go to step 3.

1. Start engine and bring to operating temperature to 85°C (185°F).

1. Does engine reach operating temperature 85°C (185°F).
   1. Yes; Go to step 5.
   1. No; replace the engine cooling system thermostat. 

1. Shut engine OFF.

1. Disconnect inlet and outlet coolant temperature sensors.

1. Inspect inlet and outlet coolant temperature sensors, harness connectors for bent, spread or corroded pins.
   1. If pin damage is found, repair as necessary.
   1. If no pin damage is found, Go to step 8.

1. Check coolant sensor resistance; refer to chart for specifications, replace sensor which is out of range.

   Coolant Sensor Resistance Chart
   Temp °C	Temp °F	Resistance (Ω) Nominal	Resistance Low (Ω)	Resistance High (Ω)	Nominal Voltage (V)	Voltage Low (V)	Voltage High (V)
   0	32	5872.8	5496.4	6249.2	2.56	2.51	2.61
   10	50	3769	3640.3	3897.7	2.37	2.33	2.41
   20	68	2480.7	2260.0	2701.4	2.14	2.05	2.22
   30	86	1693.2	1613.4	1773.0	1.89	1.83	1.95
   35	95	1401.1	1338.4	1463.8	1.75	1.69	1.81
   40	104	1166.8	1117.5	1216.1	1.62	1.56	1.67
   50	122	829.5	798.2	860.8	1.36	1.30	1.41
   60	140	593.8	574.5	613.1	1.12	1.07	1.17
   70	158	435.4	423.1	447.7	0.91	0.86	0.95

1. Visually inspect entire exhaust system for signs of leaks or damage. Are there any leaking or damaged exhaust components?
   1. Yes; repair as necessary.
   1. No; Go to step 2.

1. Connect DiagnosticLink^® .

1. Using the Selective Catalytic Reduction (SCR) voltage service routine, monitor the Diesel Oxidation Catalyst (DOC) inlet pressure (pin 87) and DPF outlet pressure (pin 72) voltages with the key ON, engine OFF.

1. Are the DOC inlet and DPF outlet pressure sensors voltages between .44 to .56 volts?
   1. Yes; Go to step 6.
   1. No; Go to step 5.

1. Inspect electrical connections between suspect sensor connector and Aftertreatment Control Module (ACM) for bent, spread, or corroded pins. Is there any damage found?
   1. Yes; repair as necessary.
   1. No; replace the sensor with the voltage reading outside of the 0.44-0.56 volts.

1. Inspect the DOC and DPF pressure sensor tubes and elbows for leaks, kinks, or blockages. Were any leaks, kinks or blockages found?
   1. Yes; repair as necessary.
   1. No; Go to step 7.

1. Start the engine and run a Parked Regen. During the last 10% of the parked regen period, is the Selective Catalyst Reduction (SCR) inlet temperature more than 38°C (68.4°F) lower than SCR outlet temperature?
   1. Yes; Go to step 8.
   1. No; Go to step 9.

1. Perform a low temperature Aftertreatment Device (ATD) check using DiagnosticLink to check for a drifted temperature sensor.  Are the SCR inlet and SCR outlet temperatures within 25°C (45°F) during the last five minutes of this test?
   1. Yes; replace the DOC/SCR module. This indicates an internal failure of the DOC/SCR module.
   1. No; replace the drifted SCR temperature sensor. Go to step 9.

1. During the parked regen, does either the DOC inlet pressure or DPF outlet pressure sensor drop to 0.0 psi?
   1. Yes; replace the failed sensor.
   1. No; clear fault and release unit. The code likely occurred after extended idle and soot buildup has cleared.