John Deere Engines SPN111FMI1 Fault Code: Engine Coolant Level Low
Also called Coolant Level Extremely Low, Engine Coolant Level Alarm Switch Activated at High Coolant Temperature, Engine Coolant Level Alarm Switch Activated at High Coolant Temperature, Engine Coolant Level Extremely Low
Engine Coolant Level Low · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
SPN 111 FMI 1 means the John Deere ECU has detected a low engine coolant condition, either through a loss of coolant temperature switch closing to ground or through a low coolant level sensor signal. This triggers engine protection, and on most setups the engine will derate and can shut down within 30 seconds if the condition doesn't clear. Treat it as a stop-and-check coolant level situation, not something to drive through.
Critical severity. This code activates engine protection. Depending on how the ECU is configured, the engine will derate at 20% per minute, 40% per minute, or 50% per minute and can shut down after 30 seconds if the switch does not reset. Running the engine low on coolant risks overheating and serious internal damage, so this is treated as critical even though the code itself is just a signal.
What does John Deere Engines error code SPN111FMI1 mean?
SPN 111 FMI 1 is John Deere's fault code for a low or lost engine coolant condition. It can be triggered two different ways depending on how the engine is set up: by a loss of coolant temperature switch closing its contacts, or by the ECU reading a low coolant level over CAN from another controller or from a dedicated coolant level sensor.
The loss of coolant temperature switch is a normally open, temperature sensitive switch mounted near the back of the cylinder head. When coolant is at the proper level, the switch's sensing tip stays submerged and cool, keeping the contacts open. If coolant drops below that point, the tip is exposed to hot air instead of coolant, its temperature rises, and the contacts close. That closure gives the ECU continuity to ground on the external shutdown/derate input terminal, which the ECU reads as a low coolant condition.
Some John Deere OEM setups use a trimmable option that lets the switch be wired as normally open or normally closed, so the ECU has to be programmed to match the switch type in use. Regardless of which method is used, the underlying concern is the same: the engine may not have enough coolant to be cooled properly, so the ECU steps in to protect it.
This code is related to, but distinct from, a coolant temperature sensor reading an extreme high temperature that looks like the sensor is no longer submerged. That condition is tracked separately, but it stems from the same root problem, low or lost coolant.
What triggers a John Deere Engines SPN111FMI1 code?
The code sets when the loss of coolant temperature switch contacts close, giving the ECU continuity to ground through the external shutdown/derate input terminal. On applications using a coolant level sensor or CAN-based coolant level message instead of the switch, the code sets when the ECU detects a low coolant level signal from that source.
Common causes of SPN111FMI1
- Incorrect or low coolant level, including external or internal coolant leaks
- Bad, damaged, dirty, or poorly positioned terminals or connectors at the ECU 30-way connector, at the loss of coolant temperature switch, or at the coolant level sensor
- Open or short in the wiring harness between the switch/sensor and the ECU
- Short to ground in the loss of coolant temperature input circuit
- Bad loss of coolant temperature switch or bad coolant level sensor
- Bad ECU (listed as a possible cause on some control units)
How to troubleshoot John Deere Engines SPN111FMI1: first checks
- Check the engine coolant level first, since low or leaking coolant is the most direct cause of this code
- Look for visible external coolant leaks at hoses, the radiator, water pump, and other fittings, and check for signs of internal leaks such as coolant loss with no visible external leak
- Without disconnecting anything, visually inspect the ECU connector and the loss of coolant switch or coolant level sensor connector for contamination, damage, or poor terminal positioning
- Inspect the wiring harness between the ECU and the switch/sensor for chafing, pinches, or corrosion that could cause an open or a short to ground
- Use a proper connector adapter test kit such as John Deere's JT07328 to check circuits at the connectors, since forcing probes into the terminals can damage them
- Confirm which type of switch is fitted (normally open or normally closed) and make sure the ECU is programmed to match, since this is a trimmable option on OEM applications
How the code clears
No separate reset procedure is listed for this code beyond correcting the low coolant condition itself. If the loss of coolant temperature switch resets, meaning coolant covers the sensing tip again and the contacts reopen, within 30 seconds of the code setting, the shutdown does not occur. Once coolant level and the switch or sensor circuit are confirmed good, engine protection should stop derating power and the code can be expected to clear on its own as the ECU sees the fault condition go away.
Frequently asked questions
What does John Deere SPN 111 FMI 1 mean?
It means the ECU has detected a low engine coolant condition. This can come from a loss of coolant temperature switch closing to ground, or from a coolant level sensor or CAN message indicating the coolant is low.
Will my engine shut down if this code is active?
It can. If the ECU is configured with the shutdown feature and the loss of coolant temperature switch does not reset within 30 seconds, the engine will shut down. If shutdown is not enabled, the engine will instead derate power without stopping.
How much will the engine derate with SPN 111 FMI 1 active?
It depends on the ECU configuration. Some derate at 20% per minute until power is reduced by 40% of rated power, some derate at 20% per minute down to 60% of full power, some derate at 40% per minute down to 60% of full power, and others derate at 50% per minute down to 50% of full power.
Is this code always caused by actually being low on coolant?
Not necessarily. While low coolant or a coolant leak is a common cause, the code can also be triggered by bad terminals or connectors, an open or short in the wiring harness, a short to ground in the input circuit, or a failed switch or sensor even when coolant level is fine.
Can I just top off the coolant and keep driving?
Topping off coolant is the right first step, but you should also check for leaks and inspect the wiring and connectors at the switch or sensor and at the ECU. If the code returns after topping off, the switch, sensor, or wiring likely needs attention, not just more coolant.
What is the loss of coolant temperature switch and where is it located?
It is a normally open, temperature sensitive switch mounted near the back of the cylinder head. Its tip stays submerged in coolant during normal operation. When coolant drops and the tip is exposed to hot air, the switch contacts close and signal the ECU.
Why do some John Deere engines use a sensor instead of a switch for this code?
Some applications use a dedicated coolant level sensor or a CAN message from another controller to report coolant temperature and level, instead of relying on the physical loss of coolant switch. Either method can set SPN 111 FMI 1 if a low coolant condition is detected.