SPN 109 FMI 3: coolant pressure, voltage high or shorted high
Coolant pressure circuit: voltage above normal, or shorted to high source. Type another SPN and FMI to check it.
Coolant pressure circuit: voltage above normal, or shorted to high source. An electrical fault (usually an open wire, a bad plug, or a wire shorted to power), not a reading out of range.
- Look at the plug and harness at the coolant pressure for rubbed, pinched, wet or green pins.
- Check supply voltage and ground at the plug (or the coil resistance on a valve or heater).
- If the wiring is good, replace the part.
Paste the whole line if you like: "SPN 3251 FMI 0", "3251/0" or Deere's "003251.00". Plain-words guidance; the service manual wins.
What SPN 109 FMI 3 means
Coolant pressure circuit: voltage above normal, or shorted to high source. An electrical fault (usually an open wire, a bad plug, or a wire shorted to power), not a reading out of range.
FMI 3: voltage high or shorted high
Signal voltage too high. Usually an open wire, a bad plug, or a wire shorted to power. (SAE J1939-73: Voltage above normal, or shorted to high source.)
How urgent it is
Fix it today. Fix it this shift or today. Left alone it tends to become a derate.
What to check first
- Look at the plug and harness at the coolant pressure for rubbed, pinched, wet or green pins.
- Check supply voltage and ground at the plug (or the coil resistance on a valve or heater).
- If the wiring is good, replace the part.
Plain-words guidance for a foreman, not a repair procedure. Makers add their own codes and steps; the machine's service manual wins.
Other FMIs for SPN 109
| Code | What failed | Urgency |
|---|---|---|
| SPN 109 FMI 4 | voltage low or shorted low | Fix it today |
Next time, Dozer catches the code when it fires.
Plug a CAN logger into the machine's J1939 port, or connect the telematics you have. When a code fires, Dozer opens a repair ticket with the meaning, how urgent it is and what to check.
- The code, the machine and its hours on one ticket
- Severity sorted: keep working, plan a stop, or stop now
- The mechanic gets the checklist before they drive out
- Repeat codes on the same machine get flagged
LIVE EX-04 · SPN 3251 FMI 0 · plan a stop today Photo is an AI-generated stand-in, not a customer site.
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Questions crews ask
What does SPN 109 FMI 3 mean?
Coolant pressure circuit: voltage above normal, or shorted to high source. An electrical fault (usually an open wire, a bad plug, or a wire shorted to power), not a reading out of range. FMI 3 means: Signal voltage too high. Usually an open wire, a bad plug, or a wire shorted to power.
Can I keep running with SPN 109 FMI 3?
Fix it today. Finish what's safe to finish, then fix it this shift. Ignoring it usually turns into a derate or a bigger repair. If the machine derates or the stop lamp is on, stop.
What should I check first for SPN 109 FMI 3?
Look at the plug and harness at the coolant pressure for rubbed, pinched, wet or green pins. Check supply voltage and ground at the plug (or the coil resistance on a valve or heater). If the wiring is good, replace the part.
How do I clear SPN 109 FMI 3?
Fix the cause first. Most codes go inactive by themselves once the condition is gone and the engine has run a key cycle or two. Clearing it with a service tool without a fix only hides it until it comes back.
Which machines show SPN 109 FMI 3?
Any diesel that speaks SAE J1939: excavators, dozers, loaders, haul trucks, generators and on-road trucks with Cat, Cummins, Deere, Komatsu, Volvo, Kubota, Perkins and other engines. The SPN means the same thing on all of them; the fix steps can differ, so check the service manual.
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