Cummins fault code 2789
Engine Coolant Temperature: reading below normal (moderately severe)
What it means
Cummins' description: Engine Coolant Temperature - Data Valid But Below Normal Operating Range - Moderately Severe Level.
SPN 110 is Engine Coolant Temperature. FMI 18 means the value is clearly below normal operating range. It's the middle 'low' level.
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
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 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
The sensor reading itself is out of range or the condition is real, so look at the system:
- Low coolant from a leak
- Radiator or charge air cooler blocked with dirt or bugs
- Fan clutch or fan not engaging
- Stuck thermostat
- Failing water pump
- Head gasket or EGR cooler pushing exhaust into the coolant
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: 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
- 144 SPN 110 FMI 3
Engine Coolant Temperature 1 Sensor Circuit: circuit voltage high / shorted high - 145 SPN 110 FMI 4
Engine Coolant Temperature 1 Sensor Circuit: circuit voltage low / shorted low - 146 SPN 110 FMI 16
Engine Coolant Temperature: reading above normal (moderately severe) - 151 SPN 110 FMI 0
Engine Coolant Temperature: reading above normal (most severe) - 334 SPN 110 FMI 2
Engine Coolant Temperature: erratic or intermittent signal - 1847 SPN 110 FMI 14
Engine Coolant Temperature: special instructions - 2646 SPN 110 FMI 31
Engine Coolant Temperature: condition exists - 2659 SPN 110 FMI 31
Engine Coolant Temperature: condition exists
Related Engine cooling codes
- 2448 SPN 111 FMI 17
Coolant Level: reading below normal (least severe) - 3243 SPN 3060 FMI 18
Engine Cooling System Monitor: reading below normal (moderately severe) - 3366 SPN 111 FMI 18
Coolant Level: reading below normal (moderately severe) - 3613 SPN 111 FMI 9
Coolant Level Sensor: abnormal update rate - 611 SPN 1383 FMI 31
Engine Shut Down Hot: condition exists - 422 SPN 111 FMI 2
Coolant Level: erratic or intermittent signal
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 2789 mean?
Cummins fault code 2789 is J1939 SPN 110 FMI 18: Engine Coolant Temperature - Data Valid But Below Normal Operating Range - Moderately Severe Level. In plain terms: engine coolant temperature: reading below normal (moderately severe).
Can I keep driving with Cummins code 2789?
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 2789?
SPN 110 identifies the part or system (Engine Coolant Temperature). FMI 18 describes the type of failure: reading below normal (moderately severe).
What usually causes Cummins code 2789?
The most common causes are: low coolant from a leak; radiator or charge air cooler blocked with dirt or bugs; fan clutch or fan not engaging.
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.