CAT Engine 1104 Fault Code: Engine Coolant Temperature short to ground
Also called Coolant Temp Signal Shorted to Ground, Coolant Temperature Signal Shorted To Ground, Engine Coolant Temperature : Voltage Below Normal, Engine Coolant Temperature Sensor - Voltage Below Normal, Engine Coolant Temperature Sensor : Voltage Below Normal, Engine Coolant Temperature Sensor Voltage Below Normal, Engine Coolant Temperature Sensor voltage below normal, Engine Coolant Temperature Sensor: Voltage Below Normal, Engine Coolant Temperature Sensor:Voltage Below Normal, Engine Coolant Temperature Short to Ground, Engine Coolant Temperture Sensor : Voltage Above Normal
Engine Coolant Temperature short to ground · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT fault code 1104 (SPN 110 / FMI 4) means the ECM sees the engine coolant temperature signal voltage stuck at or below 0.2 VDC for a set time, which it reads as a short to ground. The ECM flags coolant temperature as invalid, substitutes a default value, and the engine may run poorly, misfire, or lose power until the wiring or sensor is fixed.
Medium severity. The engine keeps running on a default coolant temperature value, so it is not an immediate shutdown code, but running on false data can cause white smoke, misfires, poor cold running, low power, or reduced rpm and can prevent the engine from entering cold mode or engaging the cooling fan properly. Diagnose it within the shift rather than ignoring it.
What does CAT Engine error code 1104 mean?
Fault code 1104 relates to the engine coolant temperature sensor circuit on CAT C10 through C32 engines (SPN 110 / FMI 4). The coolant temperature sensor is a two-terminal passive sensor that feeds a signal back to the ECM so it knows how hot or cold the engine is running. The ECM uses that signal to manage cold mode operation, idle strategy, fan engagement, and injection timing.
When the ECM sees the signal voltage drop to at or below 0.2 VDC for a sustained period, it interprets this as the signal wire shorted to ground rather than a real cold-engine reading. Since a genuinely cold engine would still produce some voltage above that near-zero floor, the ECM treats this as an electrical fault, not real temperature data.
Once the code is active, the ECM stops trusting the sensor. It logs the fault, flags coolant temperature as invalid data, and substitutes a default value so the engine can keep running. Depending on the specific control strategy on the engine, that default may be -40 °C (-40 °F) or 90 °C (194 °F), and the engine will not properly enter cold mode based on real data.
What triggers a CAT Engine 1104 code?
The ECM sets this code when engine coolant temperature signal voltage is at or below 0.2 VDC. Depending on the specific engine control strategy, this must persist for 0.24 seconds, 1 second, or 8 seconds before the code goes active, and the ECM must have already been powered up for 2 seconds or 3 seconds (strategy dependent) before the check applies. On some control strategies the code is only logged as active history if the engine has already been running more than 7 minutes. Some strategies also require that a related diagnostic code (such as 262-03 or 262-04, or a 168-X code) is not already active before this code can set.
Common causes of 1104
- Damaged, corroded, or loose connectors and wiring at the coolant temperature sensor or ECM connector
- Coolant temperature signal wire shorted to ground
- Short circuit between the sensor's signal wire and the analog sensor common (return) wire
- Short in the harness to battery voltage or other wiring damage from abrasion, corrosion, or a pinch point
- Faulty or poorly seated pins and sockets in the connectors, or a poor connection between a wire and its terminal
- A faulty or worn-out engine coolant temperature sensor that needs replacement
- An open circuit in the 5-volt supply wire, or a short between the 5-volt supply and the signal wire (on sensors that use ECM-supplied voltage)
- A defective ECM (less common, but listed as a possible cause across the diagnostic procedures)
How to troubleshoot CAT Engine 1104: first checks
- Pull up the active and logged codes on the diagnostic scan tool or lamp and confirm 1104 (SPN 110 / FMI 4) is present, and check whether any related codes (such as 262-03, 262-04, or a 168-X code) are also active, since these can block 1104 from registering
- With the engine off and key on, inspect the coolant temperature sensor connector and the ECM connector (J1/P1) for corrosion, moisture, bent pins, or a connector that is not fully seated
- Trace the harness between the sensor and the ECM looking for chafed, pinched, or abraded wiring, especially near mounting points or areas prone to rubbing
- Check for a short between the signal wire and ground, and a short between the signal wire and the sensor common/return line, using a multimeter with the connector disconnected
- If the sensor uses a 5-volt supply, verify that supply wire has no open circuit and is not shorted to the signal wire
- Test the sensor itself against its known resistance/voltage behavior if a bench or reference specification is available, and replace it if it fails to respond correctly to temperature change
- If wiring and sensor check out clean, suspect the ECM as a last resort since it is listed as a possible cause but is the least common failure point
How the code clears
No separate clearing step is listed beyond fixing the underlying wiring or sensor fault. Once the short to ground is repaired or the sensor is replaced and the signal voltage returns to a normal range, the ECM should stop logging the active fault. Clear the logged code with a diagnostic scan tool and verify it does not return during a test run.
Affected models and serial ranges
1104 appears in our records across 10 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C10 | Serial range not listed in source records |
| C11 | Serial range not listed in source records |
| C12 | Serial range not listed in source records |
| C13 | Serial range not listed in source records |
| C15 | Serial range not listed in source records |
| C16 | Serial range not listed in source records |
| C175 | Serial range not listed in source records |
| C18 | Serial range not listed in source records |
| C27 | Serial range not listed in source records |
| C32 | Serial range not listed in source records |
Frequently asked questions
What does CAT code 1104 mean?
It means the ECM has detected the engine coolant temperature sensor signal voltage at or below 0.2 VDC, which it interprets as a short to ground rather than a valid temperature reading. The ECM then uses a default coolant temperature value instead of the real sensor signal.
Can I keep driving or operating with code 1104 active?
The engine will typically keep running because the ECM substitutes a default coolant temperature value, but you may notice engine misfires, low power, reduced engine speed, poor cold running, or white smoke. It is best to diagnose the fault within the shift rather than running on it long term.
What default coolant temperature does the ECM use when this code is active?
Depending on the control strategy, the ECM may default to -40 °C (-40 °F) or 90 °C (194 °F) for coolant temperature, or in some cases fall back on the last valid reading or the intake manifold air temperature if that is available.
Will this code stop the engine from going into cold mode?
Yes. With the coolant temperature signal flagged as invalid, the engine will not properly enter cold mode operation, which can affect startability, white smoke control, and warm-up behavior.
What usually causes a coolant temperature sensor to short to ground?
The most common causes are damaged or corroded connectors, chafed or pinched wiring in the harness, a short between the signal wire and ground or the sensor common wire, or a worn-out sensor. A defective ECM is possible but far less common.
Does this code affect the cooling fan?
On some control strategies, if the coolant temperature signal fault stays active for more than 8 seconds, the ECM will activate the cooling fan as a precaution since it cannot verify the actual coolant temperature.
Is there a specific reset procedure for code 1104?
No separate clearing step is listed beyond repairing the wiring, connector, or sensor issue causing the short to ground. After the repair, clear the code with a scan tool and confirm it does not reset during operation.