Air Assist Pressure Is Low
Use this procedure to troubleshoot a low dosing air assist pressure. Also, use this procedure if one of the following event codes is active or logged.
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J1939 Code and Description | CDL Code and Description | Comments |
---|---|---|
4335-17
Aftertreatment #1 SCR Dosing Air Assist Absolute Pressure : Low - least severe (1) |
E964 (1)
Low Aftertreatment #1 SCR Dosing Atomization Air Assist Pressure |
The air pressure is below the trip point for the programmed delay time.
Dosing is disabled until the pressure is correct. The code is logged. |
4335-18
Aftertreatment #1 SCR Dosing Air Assist Absolute Pressure : Low - moderate severity (2) |
E964 (2)
Low Aftertreatment #1 SCR Dosing Atomization Air Assist Pressure |
The air pressure is below 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
- Leaks
- Air pressure
- Sensor
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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 for Air Leaks A. Remove electrical power from the engine. B. Inspect the air supply lines to the dosing cabinet and inside the dosing cabinet for leaks. |
Leaks |
Result: An air leak was found. Repair: Repair the air leak. Proceed to Test Step 5. Result: An air leak was not found. Proceed to Test Step 3. |
3. 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 less 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 4. |
|
4. Check the Aftertreatment #1 Supply Air Pressure Sensor A. Apply electrical power to the engine. B. Connect Cat ET. C. Use Cat ET to monitor the following pressures: - "Aftertreatment #1 Supply Air Pressure" - "Aftertreatment #1 DEF Dosing Pressure" |
Sensor |
Result: The pressure sensors are within Proceed to Test Step 5. Result: The pressure sensors are not within Repair: Replace the "Aftertreatment #1 Supply Air Pressure" sensor. If the problem is not resolved, proceed to Test Step 5. |
5. Check the Air Assist Valve 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 acceptable range of the air pressure is The system is working properly. Return to service. Result: The air pressure is less 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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