C175-16 Locomotive Engine Caterpillar

NOx Conversion Is Low

Usage:

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 - least severe (1)	N/A	The Diesel Exhaust Fluid (DEF) has a high concentration.
3516-18 Aftertreatment #1 DEF Concentration : Low - least severe (1)	N/A	The DEF has a low concentration.
4364-17 Aftertreatment #1 SCR Catalyst Conversion Efficiency : Low - least severe (1)	E1309 (1) Low Aftertreatment #1 SCR Catalyst Conversion Efficiency	The NOx conversion across the Selective Catalyst Reduction (SCR) catalyst is lower than expected.
4364-18 Aftertreatment #1 SCR Catalyst Conversion Efficiency : Low - moderate severity (2)	E1309 (2) Low Aftertreatment #1 SCR Catalyst Conversion Efficiency	The NOx conversion across the SCR catalyst is lower than expected.

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Table 2
Required Tools		Qty
464-1955	Tool Case As	1

Probable Causes

Codes
DEF quality
DEF pump
DEF pressure line
Urea deposits
Sensor

Recommended Actions

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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. Look for active codes that are associated with the system for the event code.	Codes	Result: An associated code is active. Repair: Troubleshoot any associated codes before continuing with this test. Result: A code is active or logged. Proceed to Test Step 2.
2. Check the Diesel Exhaust Fluid (DEF) Quality A. Use 431-7087 Tool Gp (DEF Refractometer) to measure the DEF quality. Refer to Testing and Adjusting, "Diesel Exhaust Fluid Quality - Test" for additional information.	DEF	Result: The DEF quality is within the acceptable range. Proceed to Test Step 3. Result: The DEF quality is not within the acceptable range. Repair: Drain the DEF fluid from the tank. Refill the tank with DEF meets ISO 22241 standard. Proceed to Test Step 3.
3. Check the DEF Pump Note: Shore power must be present while performing this step in order for the DEF pump to have power. A. Remove electrical power from the engine. B. Remove the DEF line that runs to the DEF injector from the dosing cabinet. C. Install the DEF line attachment included in the 464-1955 Tool Case As. D. Run the DEF line into the container included in the 464-1955 Tool Case As. E. Apply electrical power to the engine. F. Connect Cat ET. G. Use Cat ET to perform the following test: - "DEF Dosing System Accuracy Test" Note: While performing this test, the test hose can contain up to an extra 140 mL (4.76 oz) of fluid. If this fluid drains into the test container, the total volume of DEF will be 2145 ± 200 mL.	2 L ± 200 mL	Result: The test returned 2 L ± 200 mL of DEF. Proceed to Test Step 4. Result: The test did not returned 2 L ± 200 mL of DEF. Repair: Replace the DEF pump. Proceed to Test Step 6.
4. Inspect the Exhaust for Urea Deposits A. Remove electrical power from the engine for 1 minute. B. Remove the DEF injector from the exhaust. C. Inspect the exhaust for signs of urea deposits that block the DEF injector, the mixer, and the SCR catalyst. Note: Urea deposits in the exhaust are normal and should only be removed if deposits are blocking DEF flow from the injector or blocking exhaust flow in the mixer or SCR catalyst.	Urea Deposits	Result: There are urea deposits that are blocking exhaust or DEF flow. Repair: Remove the urea deposits from the exhaust system. Proceed to Test Step 6. Result: There are no urea deposits that are blocking exhaust or DEF flow. Proceed to Test Step 5.
5. Replace the NOx Sensors A. Remove electrical power from the engine. B. Replace the NOx sensors.	Sensors	Repair: The NOx sensors were replaced. Proceed to Test Step 6.
6. Operate the Engine A. Apply electrical power to the engine. B. Start the engine. C. Connect to Cat ET. D. Use Cat ET to monitor the following temperature: - "Aftertreatment #1 SCR Inlet Temperature" E. Operate the engine with the "Aftertreatment #1 SCR Inlet Temperature" above 250° C (482° F) for a minimum of 30 minutes.	Codes	Result: A code is not active. 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).