SPN 91 FMI 13 – J1939 EEC2 Message is missing or not available Fault Code (Symptoms, Causes & Fix)

Mar 15, 2026

The SPN 91 FMI 13 fault code indicates a communication issue where the J1939 EEC2 message is missing or not available. This diesel engine fault code suggests that the Engine Control Module (ECM) is not receiving the necessary data from the J1939 data link, which is crucial for engine management and diagnostics.

What SPN 91 FMI 13 Means

SPN 91 FMI 13 fault code is related to the J1939 communication network, specifically the EEC2 message, which is essential for the ECM to perform its functions. When this message is missing, it means the ECM cannot access critical data needed for engine operation, potentially leading to performance issues.

Common Causes of This Fault Code

Faulty ECM
Damaged or corroded J1939 data link wiring
Loose or damaged connectors
Faulty terminating resistor
Interference from other electronic devices

Symptoms Drivers May Notice

When the SPN 91 FMI 13 fault code is active, drivers may notice symptoms such as engine hesitation, reduced power, or unexpected engine derate. The Check Engine Light may also illuminate, indicating a communication issue that requires attention.

How Technicians Diagnose This Fault

Technicians begin diagnosing the SPN 91 FMI 13 fault by performing a visual inspection of the J1939 data link wiring and connectors for any signs of damage or corrosion. Next, they check for secure connections and measure the resistance across the data link to verify the integrity of the terminating resistors. Using a multimeter, they check for proper voltage and continuity in the data link circuit. Finally, they connect a diagnostic tool to ensure other modules are communicating properly, confirming the ECM's ability to receive data.

Common Misdiagnosis

A common misdiagnosis with SPN 91 FMI 13 is replacing the ECM without verifying the integrity of the data link. Technicians may also mistakenly assume a sensor failure without checking the communication lines or overlook intermittent connection issues caused by vibration.

Can You Keep Driving?

While it may be possible to continue driving with the SPN 91 FMI 13 fault code active, it is not advisable. The communication issue can lead to engine derate or protection mode, affecting performance and potentially causing further damage. It is best to address the fault promptly to avoid these risks.

Mechanic's Diagnostic Tip

When troubleshooting SPN 91 FMI 13, always start with a thorough inspection of the J1939 data link wiring and connectors. Pay special attention to areas prone to vibration, as intermittent connection issues are common in these spots. Confirm the integrity of the terminating resistors before considering ECM replacement.

Frequently Asked Questions

Q: What tools are needed to diagnose SPN 91 FMI 13?
A: A multimeter and a diagnostic scan tool are essential for checking voltage, continuity, and communication between modules.

Q: Can a faulty sensor cause SPN 91 FMI 13?
A: While a faulty sensor itself may not directly cause this code, issues with the communication lines that affect sensor data transmission can trigger it.

Q: How can I prevent SPN 91 FMI 13 from occurring?
A: Regular maintenance checks on the J1939 data link wiring and connectors can help prevent this fault by ensuring all connections are secure and free from corrosion.