C175 Tier 4 Final Engines for Off-Highway Trucks Caterpillar

NOx Conversion Is Low

Usage:

793F D3T

Use this procedure to troubleshoot a low NOx conversion. Also, use this procedure if one of the following event codes is active or logged.

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Table 1
J1939 Code and Description	CDL Code and Description	Comments
3516-16 Aftertreatment #1 DEF Concentration : High - moderate severity (2)	E1365 (2) High Aftertreatment #1 DEF Concentration	The Diesel Exhaust Fluid (DEF) has a high concentration. The code is logged.
3516-18 Aftertreatment #1 DEF Concentration : Low - moderate severity (2)	E1364 (1) Low Aftertreatment #1 DEF Concentration	The DEF has a low concentration. The code is logged.
4364-2 Aftertreatment #1 SCR Catalyst Conversion Efficiency : Erratic, Intermittent, or Incorrect	E1410 (1) Invalid Aftertreatment #1 SCR Conversion Efficiency	The Aftertreatment #1 Selective Catalyst Reduction (SCR) Intake NOx Sensor and Aftertreatment #1 Outlet NOx Sensors are installed in the incorrect locations. The code is logged.
4364-17 Aftertreatment #1 SCR Catalyst Conversion Efficiency : Low - least severe (1)	E1309 (1) Low Aftertreatment #1 SCR Catalyst Conversion Efficiency	The SCR System is not able to reduce NOx in the exhaust system. The code is logged.
4419-2 Aftertreatment #2 SCR Conversion Efficiency : Erratic, Intermittent, or Incorrect	E1411 (1) Aftertreatment #2 SCR Conversion Efficiency : Erratic, Intermittent, or Incorrect	The Aftertreatment #2 SCR Intake NOx Sensor and Aftertreatment #2 Outlet NOx Sensors are installed in the incorrect locations.
4419-17 Aftertreatment #2 SCR Conversion Efficiency : Low - least severe (1)	E1310 (1) Aftertreatment #2 SCR Conversion Efficiency : Low - least severe (1)	The SCR System is not able to reduce NOx in the exhaust system.

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Table 2
Required Tools		Qty
441-0451	Kit - Test	1

Probable Causes

Codes
NOx sensors
DEF quality
DEF lines
Exhaust system
Exhaust mixer

Recommended Actions

Reference: Refer to Troubleshooting, System Overview (Aftertreatment Identification) for locating aftertreatment components if necessary.

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Table 3
Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat^® Electronic Technician (ET) to the service tool connector. B. Determine if a code is active or logged.	Codes	Result: An E1410 (1), E1411 (1), 4364-2, or 4419–2 code is active or logged. Proceed to Test Step 2. Result: For all active or logged codes other than an E1410 (1), E1411 (1), 4364-2, or 4419–2. Proceed to Test Step 3.
2. Check the NOx Sensors for Proper Installation A. Turn the keyswitch to OFF. B. Verify that the sensors are located in the correct position. Note : The "Engine Out NOx" sensor wiring has a black sheath. The "Tailpipe Out NOx" sensor wiring has a gray sheath. C. If the sensors are installed in the wrong positions, install the sensors in the correct positions. Refer to Special Instruction, REHS8151 for the correct handling procedures. D. Start the engine. E. Connect Cat ET. F. Select the "Selective Catalyst Reduction System". G. Use Cat ET to perform the following diagnostic test: -"Aftertreatment System Functional Test"	NOx Sensors	Result: The test was successful. Return to service. Result: The test was not successful and other codes were logged. Repair: Troubleshoot the logged codes. Refer to Troubleshooting for the code that became active during the test.
3. Inspect the Exhaust System A. Start the engine. B. Check the exhaust system for leaks or damage. C. Check all the exhaust connections from the turbocharger outlet to the tailpipe outlet. D. Check the exhaust system insulation for damage.	Exhaust System	Result: The exhaust system is OK. Proceed to Test Step 4. Result: The exhaust system is NOT OK. Repair: Repair or replace the damaged exhaust component. Proceed to Test Step 9.
4. Check the Diesel Exhaust Fluid (DEF) Quality A. Measure the DEF quality. Refer to Testing and Adjusting, Diesel Exhaust Fluid Quality - Test for additional information.	DEF Quality	Result: The DEF is contaminated or the concentration is not within the acceptable range. Repair: Drain the DEF from the tank. Refill the tank with DEF that meets ISO 22241 quality standards. Proceed to Test Step 9. Result: The DEF is not contaminated and the concentration is within the acceptable range. Proceed to Test Step 5.
5. Inspect the DEF Lines for Leaks A. Turn the keyswitch to the ON position. Do not start the engine. B. Connect Cat ET. C. Select the appropriate "Diesel Exhaust Fluid Control Unit (DCU)". D. Use Cat ET to perform the following diagnostic test to pressurize the system: - For Aftertreatment #1, perform the "Aftertreatment #1 DEF Dosing System #1 Prime Test" and "Aftertreatment #1 DEF Dosing System #2 Prime Test". - For Aftertreatment #2, perform the "Aftertreatment #2 DEF Dosing System #1 Prime Test" and "Aftertreatment #2 DEF Dosing System #2 Prime Test". E. Visually inspect all DEF lines from the tank to the DEF injectors. Look for pinched, damaged, or disconnected lines. F. Turn the keyswitch to OFF.	DEF Lines	Result: The lines are not leaking, damaged, pinched, or disconnected. Proceed to Test Step 6. Repair: The lines are leaking, damaged, pinched, or disconnected. Result: Repair or replace the damaged components. Proceed to Test Step 9.
6. Perform the "DEF Dosing System Accuracy Test" A. Turn the keyswitch to OFF. Allow 2 minutes to elapse before proceeding. B. Remove each of the DEF injectors from the appropriate Clean Emissions Module (CEM). C. Connect Cat ET. D. Select the appropriate DCU. E. Use Cat ET to perform the following diagnostic test on each DEF injector: - "Aftertreatment DEF Dosing Injector Accuracy Test" Refer to Testing and Adjusting, "DEF Dosing System Accuracy Test" for additional information.	DEF Dosing System Accuracy Test	Result: The amount of DEF collected is within the desired range (minimum 170 ml and maximum 190 ml). Reinstall the injector. Proceed to Test Step 9. Result: The amount of DEF collected on one or more injectors was below 170 ml. Proceed to Test Step 7. Result: The amount of DEF collected on one or more injectors was above 190 ml. A failed DEF injector has been detected. Repair: Replace the failed DEF injector. Refer to the Disassembly and Assembly manual for additional information. Proceed to Test Step 9.
7. Check the DEF Pressure Line A. Turn the keyswitch to OFF. Allow 2 minutes to elapse before proceeding. B. Remove the DEF pressure line between the DEF pump and the DEF injector that did not dose the correct amount of DEF. C. Inspect the DEF pressure line for obstructions. Flush the line with water or low-pressure air, if necessary. Note: Possible obstructions are ice, DEF deposits, or debris.	DEF Pressure Line	Result: An obstruction was found. Repair: Flush or replace the line. Proceed to Test Step 8. Result: An obstruction was not found. Repair: A failed DEF injector has been detected. Replace the failed DEF injector. Proceed to Test Step 8.
8. Perform the "DEF Dosing System Accuracy Test" Note: Test the DEF injector that was replaced or the DEF injector that is attached to the line with the blockage. A. Connect Cat ET. B. Select the "Selective Catalyst Reduction System". C. Use Cat ET to perform the following diagnostic test: -"Aftertreatment DEF Dosing System Accuracy Test" Refer to Testing and Adjusting, "DEF Dosing System Accuracy Test" for additional information.	DEF Dosing System Accuracy Test	Result: The amount of DEF collected is within the desired range (minimum 170 ml and maximum 190 ml). Repair: Replace the NOx sensors and reinstall the injector. Proceed to Test Step 9. Result: The amount of DEF collected is below 170 ml. Repair: Replace the failed DEF pump. Proceed to Test Step 10.
9. Perform the "Aftertreatment System Functional Test". A. Start the engine. B. Connect Cat ET. C. Select the "Selective Catalyst Reduction System". D. Use Cat ET to perform the following diagnostic test: -"Aftertreatment System Functional Test"	Aftertreatment System Functional Test	Result: The test was successful. Return to service.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).