SPN 3719 Freightliner: What You Need to Know

SPN 3719 is a diagnostic code that indicates a problem with the diesel particulate filter (DPF) system in a Freightliner truck. The DPF is a device that traps and burns the soot particles from the exhaust gas, reducing the emissions and improving the fuel efficiency of the engine. However, the DPF needs to be periodically cleaned by a process called regeneration, which involves heating the filter to a high temperature and burning off the accumulated soot.

There are different types of regeneration: active, passive, and parked. Active regeneration is initiated by the engine control module (ECM) when the soot level in the DPF reaches a certain threshold. The ECM injects extra fuel into the exhaust stream, which ignites and raises the temperature of the DPF. Passive regeneration occurs naturally when the exhaust gas is hot enough to burn the soot, such as during highway driving. Parked regeneration is performed manually by the driver when the active regeneration is not possible or interrupted, such as in low-speed or stop-and-go driving conditions.

The SPN 3719 code can have different failure mode indicators (FMI), which specify the nature and severity of the problem. The most common FMI codes are:

  • FMI 0: Soot level very high. This means that the DPF is almost full and needs an immediate regeneration. The driver has two minutes to initiate a parked regeneration, otherwise the engine will shut down.
  • FMI 16: Soot level high. This means that the DPF is approaching its maximum capacity and needs a regeneration soon. The driver should look for a safe place to perform a parked regeneration, or drive at a higher speed to enable active or passive regeneration.
  • FMI 31: Soot load percent condition exists. This means that the DPF has a high soot load percentage, which may affect the performance and fuel economy of the engine. The driver should follow the instructions on the instrument cluster to perform a regeneration.

The SPN 3719 code can be caused by various factors, such as:

  • Faulty DPF pressure sensor or wiring
  • Faulty DPF temperature sensor or wiring
  • Faulty DPF injector or wiring
  • Faulty DPF differential pressure switch
  • Faulty DPF regeneration valve
  • Faulty DPF regeneration lamp
  • Faulty DPF regeneration switch
  • Faulty ECM or software
  • Improper DPF installation or configuration
  • Low fuel quality or incorrect fuel type
  • Excessive idle time or low-speed driving
  • Frequent or prolonged regeneration interruptions

To troubleshoot and fix the SPN 3719 code, the following steps are recommended:

  1. Connect a diagnostic tool, such as DiagnosticLink, to the truck and read the fault codes and data.
  2. Check the DPF pressure sensor, temperature sensor, injector, wiring, and connectors for any damage, corrosion, or loose connections. Replace or repair as needed.
  3. Check the DPF differential pressure switch, regeneration valve, lamp, and switch for proper operation and alignment. Adjust or replace as needed.
  4. Check the DPF for any cracks, leaks, or damage. Replace the DPF if necessary.
  5. Check the ECM for the correct software version and configuration. Update or reprogram the ECM if necessary.
  6. Perform a manual regeneration using the diagnostic tool or the regeneration switch. Monitor the DPF pressure, temperature, and soot level during the regeneration. If the regeneration is successful, clear the fault codes and verify the repair. If the regeneration is unsuccessful or incomplete, go to the next step.
  7. Perform a DPF ash cleaning service using a qualified DPF cleaning machine. This involves removing the DPF from the truck and using compressed air and vacuum to remove the ash and other contaminants from the filter. If the DPF is too clogged or damaged, replace it with a new one.
  8. Reinstall the DPF on the truck and perform a manual regeneration. Clear the fault codes and verify the repair.

The following table summarizes the possible causes, effects, and solutions for the SPN 3719 code:

FMI Cause Effect Solution
0 DPF soot level very high Engine shutdown, increased emissions, reduced fuel economy, damage to DPF and engine Perform immediate parked regeneration, troubleshoot and fix the DPF system
16 DPF soot level high Engine derate, increased emissions, reduced fuel economy, damage to DPF and engine Perform parked regeneration as soon as possible, troubleshoot and fix the DPF system
31 DPF soot load percent condition exists Increased emissions, reduced fuel economy, damage to DPF and engine Follow the instrument cluster instructions to perform regeneration, troubleshoot and fix the DPF system
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