The Engine Control Module (ECM) monitors the differential pressure across the Diesel Particulate Filter (DPF). The differential pressure should remain within a particular range. The range is based on a map within the ECM.
| Diagnostic Trouble Codes for High Differential Pressure | |||
|---|---|---|---|
| J1939 Code | Description | Information that Relates to the Code | |
| 3251-16 | Diesel Particulate Filter Differential Pressure (bank 1) : High - Moderate Severity (2) | The differential pressure has exceeded the trip point. The trip point varies. The trip point depends on the exhaust gas temperature and the amount of exhaust gas flow. Engine power is derated. The code can not be cleared until the power to the ECM is cycled. A regeneration may be performed by using the dash switch (if equipped) or by the Caterpillar Electronic Technician (ET). |
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| 3285-16 | Diesel Particulate Filter Differential Pressure (bank 2) : High - Moderate Severity (2) | ||
| 3251-0 | Diesel Particulate Filter Differential Pressure (bank 1) : High - Most Severe (3) | The differential pressure has reached a very high level. The trip point varies. The trip point depends on the exhaust gas temperature and the amount of exhaust gas flow. Engine power is derated 100 percent. Factory passwords are required in order to clear the code. A "service test" regeneration is the only type of regeneration that can be performed. |
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| 3285-0 | Diesel Particulate Filter Differential Pressure (bank 2) : High - Most Severe (3) | ||
| Follow the troubleshooting procedure in order to identify the root cause of the problem. | |||
| Diagnostic Trouble Codes for Low Differential Pressure | |||
|---|---|---|---|
| J1939 Code | Description | Information that Relates to the Code | |
| 3251-18 | Diesel Particulate Filter Differential Pressure (bank 1) : Low - Moderate Severity (2) | The differential pressure is below the trip point. The trip point varies. The trip point depends on the exhaust gas temperature and the amount of exhaust gas flow. Engine power is derated. The Aftertreatment Regeneration Device (ARD) is deactivated. The Clean Gas Induction System (CGI) is turned off. The code can not be cleared until the power to the ECM is cycled. The following conditions can cause these codes: There is a problem with the tubing between the DPF and the sensor group for the DPF. There is a problem with the exhaust piping between the engine and the DPF. |
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| 3285-18 | Diesel Particulate Filter Differential Pressure (bank 2) : Low - Moderate Severity (2) | ||
| Follow the troubleshooting procedure in order to identify the root cause of the problem. | |||
Troubleshooting Procedure for High Differential Pressure
- If the vehicle is equipped with an ARD disable switch, verify that the switch is not disabling the ARD. Refer to the vehicle's service manual in order to determine the proper operation of the switch.
- Troubleshoot any diagnostic codes that relate to the following systems or conditions:
- Low boost
- ARD
- CGI
Troubleshoot the systems in the order that is listed above if there are diagnostic codes for more than one of the systems.
- If the ARD disable switch was not disabling the ARD and there are no problems with the systems that are listed above, perform this test step. If the switch was disabling the ARD or there was a problem with a system that is listed above, continue to the next test step.
- Remove the inlet section from the DPF. Inspect the inside of the inlet section and the front face of the DPF. Look for oil and for excessive soot.
The presence of a small amount of soot is a normal condition. Contact your local technical communicator for Caterpillar on-highway truck engines if you suspect that the amount of soot is excessive. Continue with this procedure after you have received guidance from the technical communicator.
If oil is found, inspect the outlet of the turbocharger. Contact your local technical communicator for Caterpillar on-highway truck engines if oil is found. Continue with this procedure after you have received guidance from the technical communicator. Clean the oil from the inside of the inlet section of the DPF and the front face of the DPF. Assemble the DPF. Use Cat ET to disable the ARD. Set the value of the "Data Link ARD Disable Status" configuration parameter to "Disabled" in order to disable the ARD. Run the engine at 1400 rpm for 15 minutes. Then, proceed to the next test step.
If no oil is found, leave the inlet section disconnected from the DPF. Use Cat ET to disable the ARD. Set the value of the "Data Link ARD Disable Status" configuration parameter to "Disabled" in order to disable the ARD.
Perform a manual cylinder cutout test. Manually cut out each cylinder while the exhaust is monitored. Look for the smoke to disappear as each cylinder is cut out. Replace any injectors that cause the engine to smoke and run rough when the cylinder is not cut out. Clean the inside of the inlet section of the DPF and the front face of the DPF. Assemble the DPF. Run the engine at 1400 rpm for 15 minutes.
Set the value of the "Data Link ARD Disable Status" configuration parameter to "Not Disabled" in order to enable the ARD. Then, proceed to the next test step.
- Remove the inlet section from the DPF. Inspect the inside of the inlet section and the front face of the DPF. Look for oil and for excessive soot.
- Use Cat ET to perform a stationary regeneration. Look for a 310 diagnostic code after the stationary regeneration is complete.
Return the engine to service if there is a 310 diagnostic code at the end of the stationary regeneration.
Perform the following procedure if a 310 diagnostic code is not activated at the end of the stationary regeneration:
- Increase the engine speed to 1400 rpm.
- Use Cat ET to determine the differential pressure of the DPF while the engine speed is 1400 rpm. The parameter is "Diesel Particulate Trap #1 Differential Pressure". You may need to create a new group in order to view this parameter.
- Return the engine speed to idle.
Replace the DPF if the differential pressure of the DPF is greater than
15.0 kPa (2.1 psi) during engine operation at 1400 rpm.
Troubleshooting Procedure for Low Differential Pressure
- Inspect the tubing between the sensor group and the DPF. Look for disconnected tubing, broken tubing, and cracked tubing.
- Remove both tubes. Verify that the tubes are not restricted. Install the tubes.
- Inspect the exhaust piping between the Aftertreatment Regeneration Device (ARD) and the inlet to the DPF. Look for the following problems:
- Cracked piping
- Disconnected pipes
- Loose clamps
Make the necessary repairs.
Note: If the vehicle is equipped with two diesel particulate filters, refer to Illustration 1 in order to identify the appropriate tubing.
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| Illustration 1 | g01430409 |
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Use the color of the harness connector in order to identify the appropriate tubing. | |