Selective Catalytic Reduction Retrofit Aftertreatment Caterpillar

Air Assist Pressure Is High

Usage:

SCR EF5

Use this procedure to troubleshoot a high dosing air assist pressure. Also, use this procedure if the following event code is active or logged.

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Table 1
J1939 Code and Description	Comments
4335-15 Aftertreatment #1 SCR Dosing Air Assist Absolute Pressure : High - least severe (1)	The air pressure is above the trip point for the programmed delay time. Dosing is disabled until the pressure is correct. The code is logged.

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Table 2
Associated Codes
J1939 Code	CDL Code	Troubleshooting Procedure
4335-3	3092-3	Troubleshooting, "Sensor Signal (Analog, Active) - Test"
4335-4	3092-4	Troubleshooting, "Sensor Signal (Analog, Active) - Test"
4336-5	3094-5	Troubleshooting, "Solenoid Valve - Test"
4336-6	3094-6	Troubleshooting, "Solenoid Valve - Test"

Probable Causes

Codes
Air pressure

Recommended Actions

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Table 3
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 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 Air Supply to the Dosing Cabinet A. Turn the DC breaker to the OFF position. B. Disconnect the air supply line to the dosing cabinet. C. Install a pressure gauge on the air supply line to the dosing cabinet. D. Monitor the air supply pressure from the air compressor. E. Reconnect the air supply line to the dosing cabinet.	483 kPa to 1068 kPa (70 psi to 155 psi)	Result: The air supply pressure from the air compressor is 483 kPa to 1068 kPa (70 psi to 155 psi). Proceed to Test Step 4. Result: The air supply pressure from the air compressor is greater than 1068 kPa (155 psi). Repair: There is a problem with the air supply to the dosing cabinet. For information on the air compressor, refer to the Original Equipment Manufacturers (OEM) service information. If the problem is not resolved, proceed to Test Step 3.
3. Check the Air Pressure A. Turn the DC breaker to the ON position. B. Connect Cat ET. C. Use Cat ET to perform the following override: - Set the "Aftertreatment #1 SCR Dosing Air Assist Valve Command Override" to the ON position. D. Use Cat ET to monitor the following pressure: - "Aftertreatment #1 Supply Air Pressure"	414 kPa to 469 kPa (60 psi to 68 psi)	Result: The air pressure at the "Aftertreatment #1 Supply Air Pressure" sensor is 414 kPa to 469 kPa (60 psi to 68 psi). Proceed to Test Step 5. Result: The air pressure at the "Aftertreatment #1 Supply Air Pressure" sensor is greater than 469 kPa (68 psi). Proceed to Test Step 4.
4. Check the Dosing Cabinet Outlet Air Pressure A. Turn the DC breaker to the OFF position. B. Disconnect the DEF injector air line from the dosing cabinet. C. Install a pressure gauge on the outlet of the dosing cabinet air manifold. D. Turn the DC breaker to the ON position. E. Connect Cat ET. F. Use Cat ET to perform the following override: - Set the "Aftertreatment #1 SCR Dosing Air Assist Valve Command Override" to the ON position. G. Monitor the pressure gauge and record the reading.	414 kPa to 469 kPa (60 psi to 68 psi)	Result: The air pressure at the outlet of the dosing cabinet air manifold is 414 kPa to 469 kPa (60 psi to 68 psi). Repair: Replace the "Aftertreatment #1 Supply Air Pressure" sensor. Proceed to Test Step 5. Result: The air pressure at the outlet of the dosing cabinet air manifold is greater than 469 kPa (68 psi). Repair: Replace the air pressure regulator on the air manifold. Proceed to Test Step 5.
5. Perform a "DEF Dosing System Verification Test" A. Turn the AC and DC breakers to the ON position. B. Connect Cat ET. C. Use Cat ET to perform the following diagnostic test: - "DEF Dosing System Verification Test"	Test	Result: The test was successful and the 4335-15 code cleared. 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).