Selective Catalytic Reduction Retrofit Aftertreatment

SCR Catalyst Inlet Pressure Is Low

Usage:

SCR PF3

Use this procedure to troubleshoot a low 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
6797-7 Aftertreatment #1 SCR Intake Absolute Pressure : Not Responding Properly	4054-7 Aftertreatment #1 SCR Intake Absolute Pressure : Not Responding Properly	The SCR Catalyst Intake Pressure is below the normal operating range for Aftertreatment bank #1.
6797-17 Aftertreatment #1 SCR Intake Absolute Pressure : Low - least severe (1)	E1637(1) Low Aftertreatment #1 SCR Catalyst Intake Pressure	The SCR Catalyst Intake Pressure is below the normal operating range for Aftertreatment bank #1.

Probable Causes

Codes
Sensor
Leaks
SCR catalyst

Recommended Actions

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Table 2
Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Apply electrical power to the engine. B. Connect Cat^® Electronic Technician (ET) to the service tool connector. C. 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. Verify that the Selective Catalyst Reduction (SCR) Intake Pressure Sensor is Installed A. Remove electrical power from the engine. B. Visually inspect the exhaust system to ensure that the SCR intake pressure sensor has not been tampered with or removed.	Sensor	Result: The SCR intake pressure sensor is installed in the exhaust system. Proceed to Test Step 3. Result: The SCR intake pressure sensor is not installed in the exhaust system. Repair: Install the SCR intake pressure sensor into the exhaust system. If the problem is not resolved, proceed to Test Step 3.
3. Inspect for Exhaust Leaks A. Inspect the piping between the turbine outlet and the SCR catalyst inlet for signs of leaks.	Leaks	Result: An exhaust leak was not found. Proceed to Test Step 4. Result: An exhaust leak was found. Repair: Repair or replace damaged exhaust component. If the problem is not resolved, proceed to Test Step 4.
4. Verify that the SCR Catalyst is Installed A. Remove electrical power from the engine. B. Visually inspect the exhaust system to ensure that the SCR catalyst has not been tampered with or removed.	SCR Catalyst	Result: The SCR catalyst is not installed in the exhaust system. Repair: Install the SCR catalyst into the exhaust system. Verify that the repair eliminated the problem. Result: The SCR catalyst is installed properly into the exhaust stream. Repair: Replace the SCR catalyst inlet pressure sensor. Clear the code using Cat ET. Verify that the repair eliminated the problem.

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).