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. 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 for Air Leaks A. Turn the DC breaker to the OFF position. 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. 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. |
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. Proceed to Test Step 6. |
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4. Check the Aftertreatment #1 Supply Air Pressure Sensor A. Turn the DC breaker to the ON position. 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. Proceed to Test Step 6. |
5. Check the Air Assist Valve 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" |
Result: The acceptable range of the air pressure is Proceed to Test Step 6. Result: The air pressure is less than Repair: Replace the air pressure regulator on the air manifold. Proceed to Test Step 6. |
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6. 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 4335-17 or 4335-18 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).
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