Cummins fault code 2186
Sensor Supply 4 Circuit: circuit voltage low / shorted low
What it means
Cummins' description: Sensor Supply 4 Circuit - Voltage below normal, or shorted to low source.
SPN 3512 is Sensor supply voltage 4. FMI 4 means the voltage on the circuit is lower than possible for a good sensor, usually a short to ground, a damaged harness, or a failed sensor.
The ECM needs clean, steady battery voltage, and it supplies regulated 5-volt power to many sensors. Voltage problems can cause strange codes across many systems at once.
What the lamp means
An amber (yellow) warning lamp means the engine can usually keep running, but the fault should be repaired soon, ideally the same day.
Green, yellow, red: three ways this can look
The same code can be a quick fix or a reason to shut down. Match your situation to the closest example.
Keep an eye on it
A low-voltage code after a hard winter start or after the truck sat a while, then clears.
Schedule a repair
Codes return, the truck is slow to crank, or voltage reads low while driving. Test the charging system soon.
Stop and get help
Engine dies, several systems drop out at once, or the ECM loses power. Don't run it until the power supply is fixed. It can leave you stranded.
Common causes
FMI 4 is an electrical or signal fault, so start with the circuit:
- Loose or corroded battery cables or grounds
- Blown fuse or failed power relay
- Sensor supply shorted by one bad sensor or wire
- Damaged ECM power harness
If the circuit checks out, the reading may be real. Other possibilities: weak batteries; failing alternator; parasitic drain.
What you can check before calling
- Check battery terminals and ground straps for corrosion or looseness
- Have the batteries and alternator tested
- Note if several unrelated codes appeared at the same time
Clearing the code without fixing the cause usually brings it right back, and on emissions systems it can restart derate timers. For the bigger picture, read our guide: Bad alternator or bad battery? How to tell.
Engines and sources
Listed by Cummins for: QSB 6.7, QSL 9, QSX 15, QSB 4.5, QSF 3.8, QSG 12. Cummins uses the same fault code numbers across its electronic engines, including on-highway models like the ISB/B6.7, ISL/L9 and ISX/X15, though not every code applies to every engine or software level. Source: Cummins Tier 4 Fault Codes. Always confirm with Cummins service information (QuickServe) for your engine serial number.
Same SPN, other failure types
Related Battery, power supply and sensor supply codes
- 2263 SPN 1800 FMI 16
Battery Temperature: reading above normal (moderately severe) - 2264 SPN 1800 FMI 18
Battery Temperature: reading below normal (moderately severe) - 1941 SPN 3597 FMI 4
ECU Power Output Supply Voltage 1: circuit voltage low / shorted low - 1939 SPN 3597 FMI 3
ECU Power Output Supply Voltage 1: circuit voltage high / shorted high - 1938 SPN 3597 FMI 18
ECU Power Output Supply Voltage 1: reading below normal (moderately severe) - 1777 SPN 2634 FMI 4
Power Relay Driver Circuit: circuit voltage low / shorted low
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does Cummins fault code 2186 mean?
Cummins fault code 2186 is J1939 SPN 3512 FMI 4: Sensor Supply 4 Circuit - Voltage below normal, or shorted to low source. In plain terms: sensor supply 4 circuit: circuit voltage low / shorted low.
Can I keep driving with Cummins code 2186?
Usually for a short time, if the engine runs normally and no other warnings are on. Get it diagnosed soon, because many amber codes lead to a derate if ignored. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 2186?
SPN 3512 identifies the part or system (Sensor supply voltage 4). FMI 4 describes the type of failure: circuit voltage low / shorted low.
What usually causes Cummins code 2186?
The most common causes are: loose or corroded battery cables or grounds; blown fuse or failed power relay; sensor supply shorted by one bad sensor or wire.
Diesel down in the Midlands?
We work on Cummins-powered pickups, vans and medium-duty trucks across Lexington, Columbia and the Midlands, on site at your yard or roadside.