Selective Catalytic Reduction Retrofit Aftertreatment Caterpillar

NOx Conversion Is Low

Usage:

SCR EF5

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)	E1365 (2) High Aftertreatment #1 DEF Concentration	The Diesel Exhaust Fluid (DEF) has a high concentration.
3516-18 Aftertreatment #1 DEF Concentration : Low - least severe (1)	E1364 (2) Low Aftertreatment #1 DEF Concentration	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 DEF Quality A. Use either a 431-7087 Tool Gp (DEF Refractometer) or a 360-0774 Refractometer (Brix) to measure the DEF quality. Refer to Testing and Adjusting, "Diesel Exhaust Fluid Quality - Test" for additional information. Note: The 431-7087 Tool Gp (DEF Refractometer) will not measure above 40 percent DEF concentration. The 360-0774 Refractometer (Brix) will read up to 53 percent Brix and must be used when measuring DEF concentration on marine applications.	26 percent to 51 percent DEF (25 percent to 49 percent Brix)	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 that is concentrated to either 26 percent to 51 percent DEF (25 percent to 49 percent Brix). Proceed to Test Step 3.
3. Check the DEF Pump A. Turn the AC and DC breakers to the OFF position. 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. Turn the AC and DC breakers to the ON position. 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 return 2 L ± 200 mL of DEF. Repair: Replace the DEF pump. Proceed to Test Step 6.
4 Inspect the Exhaust for Urea Deposits A. Turn the DC breaker to the OFF position 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. Turn the DC breaker to the OFF position. B. Replace the NOx sensors.	Sensors	Repair: The NOx sensors were replaced. Proceed to Test Step 6.
6. Operate the Engine A. Turn the AC and DC breaker to the ON position. 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).