Air Assist Pressure Is High
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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J1939 Code and Description | CDL Code and Description | Comments |
---|---|---|
4335-15
Aftertreatment #1 SCR Dosing Air Assist Absolute Pressure : High - least severe (1) |
N/A | 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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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" |
- Codes
- Air pressure
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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. Check the Air Supply to the Dosing Cabinet A. Remove electrical power from the engine. 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. |
Result: The air supply pressure from the air compressor is Proceed to Test Step 4. Result: The air supply pressure from the air compressor is greater than 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. |
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3. Check the Air Pressure A. Apply electrical power to the engine. B. Connect Cat ET. C. Use Cat ET to perform the following override: - "Aftertreatment #1 SCR Dosing Air Assist Valve Command Override" D. Use Cat ET to monitor the following pressure: - "Aftertreatment #1 Supply Air Pressure" |
Result: The air pressure at the "Aftertreatment #1 Supply Air Pressure" sensor is The system is working properly. Return to service. Result: The air pressure at the "Aftertreatment #1 Supply Air Pressure" sensor is greater than Proceed to Test Step 4. |
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4. Check the Dosing Cabinet Outlet Air Pressure A. Remove electrical power from the engine. 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. Apply electrical power to the engine. E. Connect Cat ET. F. Use Cat ET to perform the following override: - "Aftertreatment #1 SCR Dosing Air Assist Valve Command Override" G. Monitor the pressure gauge and record the reading. |
Result: The air pressure at the outlet of the dosing cabinet air manifold is Repair: Replace the "Aftertreatment #1 Supply Air Pressure" sensor. Verify that the repair eliminated the problem. Result: The air pressure at the outlet of the dosing cabinet air manifold is greater than Repair: Replace the air pressure regulator on the air manifold. 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).
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