Selective Catalytic Reduction Retrofit Aftertreatment

SCR Catalyst Inlet Pressure Is High

Usage:

SCR PF3

Use this procedure to troubleshoot a high Selective Catalyst Reduction (SCR) catalyst inlet pressure. Also, use this procedure if the following event code is active or logged.

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Table 1
J1939 Code and Description	CDL Code and Description	Comments
6797-15 Aftertreatment #1 SCR Intake Absolute Pressure : High - moderate severity (2)	E1476 (1) High Aftertreatment #1 SCR Catalyst Intake Pressure	The Selective Catalyst Reduction (SCR) Catalyst Intake Pressure is above the normal operating range for aftertreatment bank #1.

Probable Causes

Codes
Exhaust system
Deposits or buildup

Recommended Actions

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Turn the DC breaker to the ON position. B. Connect Cat^® Electronic Technician (ET) to the service tool Connector. C. Look for active codes that are associated.	Codes	Result: An associated code is active. Repair: Troubleshoot any engine/aftertreatment associated codes before continuing with this test. Result: A code is active or logged. Proceed to Test Step 2.
2. Inspect the Exhaust System A. Turn the DC breaker to the OFF position. B. Visually inspect the exhaust system for damage to the turbocharger out to tailpipe out, pressure lines and harness.	Exhaust System	Result: The exhaust system is OK. Proceed to Test Step 3. Result: The exhaust system is NOT OK. Repair: Repair or replace damaged exhaust components. Reference Disassembly and Assembly Manual. If the problem is not resolved, proceed to Test Step 3.
3. Run Manual Thermal Management A. Refer to the Operation Maintenance Manual, Engine Operation - Hydrocarbon Release procedure to perform the thermal management procedure. B. Check for active high SCR pressure codes.	Thermal Management Procedure	Result: There were no active high SCR codes. Repair complete. Return to Service. Result: There were active high SCR pressure codes. Proceed to Step 4.
4. Inspect the SCR Catalyst and Mixing Tube A. Turn the DC breaker to the OFF position. B. Inspect the face of the SCR catalyst, partial flow filter, and the mixing tube with a borescope for the following: - Oil - Fuel - Urea deposits	Deposits or Buildup	Result: The SCR catalyst is OK. Proceed to Step 5. Result: Inspect mixer in mixing tube for deposits. If deposits are identified, remove mixing tube and remove deposits with clean water (not sea water) and brush. Proceed to Test Step 5. Result: The SCR catalyst face has oil fuel, or soot buildup. Repair: For oil, refer to your Engine Troubleshooting related to "Exhaust System Contains Oil" for additional information. For fuel, refer to your Engine Troubleshooting related to Troubleshooting "Exhaust System Contains Fuel" for additional information. Verify that the repair eliminated the problem.
5. Run Manual Thermal Management A. After procedure is complete, allow the engine to run for 30 minutes at greater than 50% load. B. Check for active high SCR pressure codes. C. Run the Aftertreatment System Functional Test (ASFT).	Thermal Management Procedure	Result: There were no active high SCR codes. Repair complete. 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).