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SPN 513 FMI 9 – Actual Torque Signal Not Available via CAN

SPN 513 FMI 9 indicates that the actual torque signal is not available through the CAN bus, which can lead to significant performance issues. This code often arises in modern diesel engines, such as the Freightliner Cascadia equipped with a DD15 engine, and can affect the engine's ability to perform optimally.

What This Code Means

The SPN 513 FMI 9 code signifies that the engine control module (ECM) is not receiving a valid torque signal from the transmission control module (TCM) or other related modules. This absence of data can disrupt the engine's ability to calculate and manage torque, leading to performance degradation.

Why It Happens

Several factors can contribute to this code being triggered. The most common reasons include:

  • CAN Backbone Resistance Issues: A resistance check of the CAN network should show around 60 ohms. Values significantly above or below this can indicate a problem with the network.
  • Terminating Resistors: Improperly functioning or missing terminating resistors at the ends of the CAN bus can lead to signal reflections and data corruption.
  • Module Offline Behavior: If the TCM or ECM is offline due to a fault, the torque signal cannot be transmitted.
  • Intermittent Harness Faults: Damaged wiring or connectors can cause intermittent signal dropout, leading to the ECM not receiving the torque signal.

How The Truck Typically Behaves

When SPN 513 FMI 9 is active, you may notice a few symptoms:

  • The engine may enter a derate mode, limiting power and performance to prevent damage.
  • Shifting may be affected, resulting in harsh shifts or inability to shift properly.
  • Instrument cluster warnings may illuminate, indicating a problem with the engine or transmission.

Step-by-Step Diagnostic Approach

  1. Check for Other Codes: Start by scanning for additional fault codes that may provide more context.
  2. Inspect the CAN Network: Measure the resistance of the CAN backbone. Ensure it is around 60 ohms. If not, investigate potential shorts or opens.
  3. Examine Terminating Resistors: Verify that both ends of the CAN bus have properly functioning terminating resistors. Replace any faulty resistors as needed.
  4. Test Modules: Check the TCM and ECM for proper communication. If one module is offline, it may need to be reprogrammed or replaced.
  5. Inspect Wiring and Connectors: Look for any signs of wear, corrosion, or damage in the wiring harness that could cause intermittent faults.
  6. Perform a Wiggle Test: While monitoring the torque signal, gently wiggle the wiring harness to see if the signal drops, indicating a faulty connection.

Can You Keep Driving?

Driving with SPN 513 FMI 9 active is not advisable. The engine may derate, which can lead to further complications and potential damage. It's best to diagnose and resolve the issue before operating the vehicle extensively.

Frequently Asked Questions

What should I do if I can’t find a fault in the CAN network?
Consider checking for software updates for the ECM and TCM, as sometimes outdated software can cause communication issues.

How often do terminating resistors need to be replaced?
Terminating resistors should be inspected whenever you encounter communication issues, but they typically last the life of the vehicle unless damaged.

Can other codes affect SPN 513 FMI 9?
Yes, related codes, especially those involving the TCM or ECM, can provide insight into the underlying issue.