DEF Pressure Is Low
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| Diagnostic Trouble Codes for DEF Pressure Is Low | |||
|---|---|---|---|
| J1939 Code | CDL Code | Code Description
(code descriptions may vary) |
Comments |
| 4334-7 | 3090-7 | Aftertreatment #1 DEF #1 Pressure (absolute) : Not Responding Properly | DEF pump pressure is not stable after the initial priming sequence
OR The DEF pump is not able to supply DEF after the line heaters have been energized and a heating cycle has been completed |
| 4334-18 | E931 (2) | Aftertreatment #1 DEF #1 Pressure (absolute) : Low - moderate severity (2) | Diesel Exhaust Fluid (DEF) system pressure dropped below the acceptable threshold during dosing |
| 5392-31 | E1370 (2) | Aftertreatment #1 DEF Dosing Unit #1 Loss of Prime | Diesel Exhaust Fluid (DEF) system pressure was not achieved during priming |
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| Troubleshooting Test Steps | Values | Results |
|---|---|---|
1. Check the Diesel Exhaust Fluid (DEF) tank filler cap A. Clean dirt and debris from around the tank cap before removing the cap. Blockages can be caused by a build-up of dirt and debris around the cap. Note : A blocked DEF filler cap can cause a 5392-31 or E1370 (2) code. B. Remove and inspect the filler cap for blockages. |
DEF filler cap |
Result : A blockage was not found. Proceed to Test Step 2. Result : A blockage was found. Repair : Rinse the cap gently with clean water or replace the cap. Note: The cap contains a membrane so care must be taken not to damage the membrane. If the cap cannot be cleaned, the cap must be replaced. Proceed to Test Step 2. |
2. Check the Diesel Exhaust Fluid (DEF) Gauge A. Turn the keyswitch to the ON position. Do not start the engine. B. Check the current position of the DEF gauge. C. Turn the keyswitch to the OFF position. D. Clean dirt and debris from around the tank cap before removing the cap. Add or remove DEF from the DEF tank. Note : Only use DEF that meets ISO 22241 quality standards. E. Turn the keyswitch to the ON position. Do not start the engine. F. Check for a change in the DEF gauge position. |
DEF gauge |
Result : The gauge did not move by adding or removing DEF from the tank. Proceed to Test Step 3. Result : The gauge moved by adding or removing DEF from the tank. Proceed to Test Step 4. |
3. Check the Electrical Connection at the DEF Tank Header A. Turn the keyswitch to the OFF position. B. Inspect the electrical connections to the DEF tank header. Refer to Troubleshooting, "Electrical Connectors - Inspect" for further information. C. Inspect the connections for corrosion or loose wires. |
Electrical connections |
Result : The electrical connections are free of corrosion and loose wires. Repair : Replace the DEF tank header. Refer to the Disassembly and Assembly manual for the correct procedure. Proceed to Test Step 10. Result : The electrical connections are not free of corrosion or loose wires. Repair : Make the necessary repairs. Proceed to Test Step 10. |
4. Inspect the DEF Lines for Leaks A. Turn the keyswitch to the ON position. Do not start the engine. B. Connect the electronic service tool. C. Navigate to "Diagnostics Tests". D. Perform the "DEF Dosing System Verification Test" to pressurize the system. E. Inspect all DEF lines from the tank to the DEF injector. Check for pinched, damaged, disconnected, or leaking lines. F. Turn the keyswitch to the OFF position. |
DEF lines |
Result: A leaking or disconnected line was found. Repair : Repair or replace the failed DEF line. Proceed to Test Step 10. Result: A leaking or disconnected line was not found. Proceed to Test Step 5. |
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| |
| Illustration 1 | g03337472 |
| (1) DEF Suction Line Connection on the Header Unit | |
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| Troubleshooting Test Steps | Values | Results |
|---|---|---|
5. Check the Diesel Exhaust Fluid (DEF) Quality A. Measure the DEF quality. Refer to Testing and Adjusting, "Diesel Exhaust Fluid Quality - Test" for the correct procedure. |
DEF |
Result : The DEF is not contaminated. Proceed to Test Step 6. Result : The DEF is contaminated. Repair : Contact the Dealer Solutions Network (DSN) for further information. |
6. Check for Suction Line Restrictions A. Disconnect the suction line from the DEF tank header and DEF pump. B. Inspect the suction line for obstructions or damage. Also, check that the line is connected in the proper locations. Note : Possible obstructions are ice, DEF deposits, or debris. |
Restrictions |
Result: An obstruction or damage was found. Repair : Flush the line with water or low-pressure air or replace the suction line. Proceed to Test Step 10. Result: An obstruction or damage was not found. Repair : Reinstall the suction line. Proceed to Test Step 7. |
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| |
| Illustration 2 | g03763616 |
|
(2) DEF suction line filter fitting
(3) DEF pump (4) DEF pump filter cap | |
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| Troubleshooting Test Steps | Values | Results |
|---|---|---|
7. Replace the DEF Pump Filters A. Clean the area around the pump filters. B. Replace the DEF pump suction line filter fitting. Refer to Illustration 2. Tighten the new filter fitting to a torque of C. Replace the DEF pump filter. Refer to Illustration 2. Also, refer to Operation and Maintenance Manual, "Diesel Exhaust Fluid Filter - Clean/Replace" for the correct procedure. |
DEF pump filters |
Result : The DEF pump filters were replaced. Proceed to Test Step 8. |
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| |
| Illustration 3 | g03670169 |
| (5) DEF Pressure | |
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| Troubleshooting Test Steps | Values | Results |
|---|---|---|
8. Check the DEF Pump A. Turn the keyswitch to the ON position. Do not start the engine. B. Connect to the electronic service tool. C. Navigate to "Diagnostics Tests". D. Perform the "DEF Dosing System Verification Test" to pressurize the system. E. Monitor the DEF Pressure (5) on the electronic service tool during the test to see if the pressure stabilizes. Note: Ensure that the DEF pressure stabilizes within 1 minute of starting the test. |
DEF pump |
Result : The DEF pressure reached at least Proceed to Test Step 9. Result : The DEF pump did not reach at least Repair : Replace the DEF pump. Refer to Disassembly and Assembly, "Diesel Exhaust Fluid Pump - Remove and Install" for the correct procedure. Proceed to Test Step 10. |
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| |
| Illustration 4 | g03765376 |
|
Typical DEF tank header (6) DEF header (7) DEF manifold filter (8) DEF header filter | |
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| Troubleshooting Test Steps | Values | Results |
|---|---|---|
| 9. Replace the Filters and Flush the DEF Tank A. Turn the keyswitch to the OFF position. B. Remove DEF tank header (6) from the DEF tank. Refer to Disassembly and Assembly, "Manifold (DEF Heater) - Remove and Install" for the correct procedure. C. Flush the DEF tank and replace the DEF filters. Refer to Systems Operation, Testing, and Adjusting, "Diesel Exhaust Fluid Tank - Flush" for the correct procedure. |
DEF Tank Filters |
Result: The DEF tank was flushed and the filters were replaced. Proceed to Test Step 10. |
| 10. Perform an "Aftertreatment System Functional Test" A. Start the engine. B. Connect to the electronic service tool. C. Navigate to "Diagnostics Tests". D. Perform the "Aftertreatment System Functional Test". |
"Aftertreatment System Functional Test" |
Result: The test is successful. Return the unit to service. Result: The test is not successful. Proceed to Test Step 11. |
11. Perform a "DEF Dosing System Accuracy Test" A. Connect to the electronic service tool. B. Navigate to "Diagnostics Tests". C. Perform a "DEF Dosing System Accuracy Test". Refer to Systems Operation, Testing, and Adjusting, "Aftertreatment SCR System Dosing Test" for the correct procedure. |
"DEF Dosing System Accuracy Test" |
Result: The quantity collected is below specification. A failed DEF injector has been detected. Repair : Replace the DEF injector. Refer to Disassembly and Assembly, DEF Injector and Mounting - Remove and Install. Proceed to Test Step 12. Result: The quantity collected is above specification. A failed DEF injector has been detected. Repair : Replace the DEF injector. Refer to Disassembly and Assembly, DEF Injector and Mounting - Remove and Install. Proceed to Test Step 12. |
| 12. Perform an "Aftertreatment System Functional Test". A. Start the engine. B. Connect to the electronic service tool. C. Navigate to "Diagnostics Tests". D. Perform the "Aftertreatment System Functional Test". |
"Aftertreatment System Functional Test" |
Result: The test is successful. Return the unit to service. Result: The test is not successful. There are more codes. Repair : Troubleshoot the additional codes. Refer to the Troubleshooting manual for the correct procedure. Result: The test is not successful. There are no additional codes. Contact the Dealer Solutions Network (DSN). |
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