Cummins fault code 6523
Coolant Level Sensor 1 Circuit: circuit voltage low / shorted low
What it means
Cummins' description: Coolant Level Sensor 1 Circuit - Voltage below normal, or shorted to low source.
SPN 111 is Engine Coolant Level. 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 cooling system keeps the engine at operating temperature. The ECM watches coolant temperature, pressure and level, and will derate or shut down the engine to protect it from overheating.
What the lamp means
This code normally doesn't turn on a dash lamp. It's logged in the ECM for a technician to see, and often explains another active code.
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 coolant level warning that clears after topping off with the right coolant, and no leak shows up.
Schedule a repair
Coolant keeps dropping, the gauge runs hotter than normal, or the amber lamp is on. Find the leak before it becomes an overheat.
Stop and get help
Temperature gauge in the red, steam, a stop lamp, or engine protection derating power. Pull over and shut it down. Running hot can warp the head and ruin the engine.
Common causes
FMI 4 is an electrical or signal fault, so start with the circuit:
- Coolant temperature or level sensor failed
- Corroded connector
- Harness chafed against the engine or radiator
If the circuit checks out, the reading may be real. Other possibilities: low coolant from a leak; radiator or charge air cooler blocked with dirt or bugs; fan clutch or fan not engaging.
What you can check before calling
- Check the coolant level only with the engine cool
- Look for leaks, wet spots or dried coolant residue
- Clean the front of the radiator and charge air cooler
- Watch the temperature gauge and whether the fan kicks on
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: Car overheating: what to do right now, and what's causing it.
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
- 195 SPN 111 FMI 3
Coolant Level Sensor 1 Circuit: circuit voltage high / shorted high - 196 SPN 111 FMI 4
Coolant Level Sensor 1 Circuit: circuit voltage low / shorted low - 197 SPN 111 FMI 18
Coolant Level: reading below normal (moderately severe) - 235 SPN 111 FMI 1
Coolant Level: reading below normal (most severe) - 422 SPN 111 FMI 2
Coolant Level: erratic or intermittent signal - 2448 SPN 111 FMI 17
Coolant Level: reading below normal (least severe) - 3366 SPN 111 FMI 18
Coolant Level: reading below normal (moderately severe) - 3613 SPN 111 FMI 9
Coolant Level Sensor: abnormal update rate
Related Engine cooling codes
- 3243 SPN 3060 FMI 18
Engine Cooling System Monitor: reading below normal (moderately severe) - 2963 SPN 110 FMI 15
Engine Coolant Temperature: reading above normal (least severe) - 2789 SPN 110 FMI 18
Engine Coolant Temperature: reading below normal (moderately severe) - 2659 SPN 110 FMI 31
Engine Coolant Temperature: condition exists - 2646 SPN 110 FMI 31
Engine Coolant Temperature: condition exists - 1847 SPN 110 FMI 14
Engine Coolant Temperature: special instructions
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 6523 mean?
Cummins fault code 6523 is J1939 SPN 111 FMI 4: Coolant Level Sensor 1 Circuit - Voltage below normal, or shorted to low source. In plain terms: coolant level sensor 1 circuit: circuit voltage low / shorted low.
Can I keep driving with Cummins code 6523?
Usually, yes. This code doesn't normally turn on a lamp by itself, but check for other active codes that might be more serious. Look at the green, yellow and red examples on this page to judge your situation.
What is the SPN and FMI for Cummins code 6523?
SPN 111 identifies the part or system (Engine Coolant Level). FMI 4 describes the type of failure: circuit voltage low / shorted low.
What usually causes Cummins code 6523?
The most common causes are: coolant temperature or level sensor failed; corroded connector; harness chafed against the engine or radiator.
Diesel down in the Midlands?
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