What This FMI Means
FMI 9 indicates the reporting module is not receiving updated data at the expected rate from another module over the J1939 data link. The data is missing or arriving too infrequently — this is a communication fault rather than a sensor or circuit fault. The parameter value reported in the fault may be the last known value, a default value, or flagged as invalid.
J1939 messages are broadcast at defined intervals (typically every 100ms, 500ms, or 1000ms depending on the parameter). FMI 9 occurs when a receiving module detects that the expected message has not arrived within a programmed timeout window. The source address in the fault code identifies the receiving module; the transmitting module is the one to investigate.
How It Appears With SPN Codes
FMI 9 appears on SPNs whose values come from another module on the J1939 network rather than from a sensor directly wired to the reporting module. Examples include: engine torque SPNs received by the transmission controller, vehicle speed SPNs received by the ABS module, retarder status SPNs received by the engine controller, and brake system status SPNs received by the stability controller.
Multiple simultaneous FMI 9 codes across several modules often indicate a J1939 backbone issue — a wiring fault, a failed termination resistor, or a broken backbone that prevents all modules from communicating. A single isolated FMI 9 on one parameter more likely indicates the specific transmitting module has gone offline or has its own internal fault.
How to Approach Diagnosis
Use the diagnostic tool's module scan or network identification function to see which modules are responding on the J1939 network. A module that does not appear in the network scan is offline — unpowered, has failed, or its network connection is broken. The module listed as the transmitting source for the missing data is the starting point.
Inspect the J1939 network backbone wiring for the affected circuit. The J1939 standard uses a two-wire twisted pair (CAN+ and CAN-) with 120-ohm termination resistors at each end. An open in the backbone, a short between the two wires, or a missing or failed termination resistor will affect all modules connected to the affected segment. Measuring backbone resistance between CAN+ and CAN- (key-off, modules connected) should read approximately 60 ohms for a correctly wired and terminated network.
What Drivers Should Record
Note all other active fault codes, not just the FMI 9 code. The module that stopped transmitting typically has its own codes explaining why. A complete fault code report from all modules provides the full picture needed for diagnosis.
Record whether any recent electrical work occurred — module replacements, connector repairs, or accessory installations near the time FMI 9 first appeared. These events commonly introduce J1939 network wiring faults. Also note whether the problem is persistent or appears only on startup, as brief FMI 9 codes during module initialization can indicate a power-up sequencing issue rather than a permanent fault.
Related Pages
Related Fault Code Pages
Sources
- SAE J1939 Standards Collection SAE International · official · accessed 2026-05-05 · confidence medium
Source: SAE International, SAE J1939 Standards Collection. This page paraphrases factual fields only and is not a substitute for the original document.
Open source - NHTSA Manufacturer Communications Search National Highway Traffic Safety Administration · government · accessed 2026-05-05 · confidence high
Source: National Highway Traffic Safety Administration, NHTSA Manufacturer Communications Search. This page paraphrases factual fields only and is not a substitute for the original document.
Open source
FAQ
FMI 9 is common in J1939 communication codes — does it mean the other module has failed?
Not necessarily. FMI 9 (abnormal update rate) means the module reporting the fault is not receiving expected messages from another module at the expected frequency. The source module may have failed, but it could also have lost power, been disconnected, or the network connection between them may be degraded. A single-module power loss or connector fault often produces multiple FMI 9 codes from other modules on the network.
Can FMI 9 be caused by bus overload rather than a failed module?
Yes, though less commonly. A heavily loaded J1939 bus — from many modules transmitting or from an aftermarket device that is flooding the bus with messages — can delay some messages enough to trigger FMI 9 on time-sensitive parameters. More often, FMI 9 traces to a failed module, wiring damage, or a module that has lost power. Bus overload is worth considering when FMI 9 appears after new hardware was added to the network.
If FMI 9 codes appear from several modules simultaneously, where should diagnosis start?
Multiple simultaneous FMI 9 codes strongly suggest a network-level or power-supply issue rather than several modules failing at the same time. Start with: checking J1939 bus resistance (should be approximately 60 ohms between CAN-H and CAN-L with ignition off), inspecting the main J1939 harness and connectors for damage, and verifying power supply and grounds for the modules involved. A single break in the J1939 backbone is the most common explanation.