CAT Engine 1754 Fault Code: Engine Oil Temperature short to ground
Also called Engine Oil Temperature 1 - Voltage Below Normal, Engine Oil Temperature 1 : Voltage Below Normal, Engine Oil Temperature Sensor : Voltage Below Normal, Engine Oil Temperature Sensor Voltage Below Normal, Engine Oil Temperature Sensor voltage below normal, Engine Oil Temperature Short to Ground
Engine Oil Temperature short to ground · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 1754, also shown as SPN 175 FMI 4 or flash code 37, means the ECM sees the engine oil temperature (middle) sensor signal below 0.2 volts for at least eight seconds (some versions say the ECM must be powered for at least two seconds or three seconds first). The ECM treats this as a short to ground, logs the code, and substitutes the coolant temperature reading in place of oil temperature so the engine keeps running.
Medium severity. The engine will keep running because the ECM substitutes a default or coolant-based value for oil temperature, but you lose accurate oil temperature monitoring and may see hard starting, rough idle, or excessive white smoke. Diagnose it within the shift rather than ignoring it long term.
What does CAT Engine error code 1754 mean?
Code 1754 (SPN 175, FMI 4) fires when the Electronic Control Module (ECM) sees the signal voltage from the engine oil temperature sensor (middle) drop below 0.2 volts for at least eight seconds. The ECM reads this low, near-zero voltage as a short to ground in the sensor circuit rather than a real temperature reading.
This sensor is a simple two-terminal device. It does not get supply voltage from the ECM. Terminal 2 ties into a common sensor ground shared by other temperature sensors (coolant, oil end, intake manifold air), and the ECM watches terminal 1 for the actual signal. Because of that shared common line, a wiring or connector problem here can sometimes affect readings on the other temperature sensors too.
Once the fault sets, the ECM flags oil temperature as invalid and substitutes the engine coolant temperature value in its place. If the coolant sensor has also failed, the ECM falls back to a fixed default: 65 °C (149 °F) if the engine is running, or -10 °C (14 °F) if the engine is not running.
What triggers a CAT Engine 1754 code?
The ECM sets this code when signal voltage from the engine oil temperature sensor (middle) reads below 0.2 volts for at least eight seconds. Depending on the specific ECM software, the module must also have been powered for at least two seconds (or in one version, at least three seconds) before the code can log.
Common causes of 1754
- Faulty, corroded, or damaged connectors or wiring at the sensor or engine harness
- A short circuit in the signal wire, pulling it down to ground
- Seals out of place at the connector, allowing moisture intrusion
- A general problem in the engine harness itself, including the faulty engine harness connector
- An intermittent connection issue that only shows up under vibration or temperature change
- A failed engine oil temperature sensor that needs replacement
- A faulty ECM, though this is listed last since wiring and sensor problems are far more common
How to troubleshoot CAT Engine 1754: first checks
- Check the diagnostic scan tool or Cat Electronic Technician (ET) status screen. It should show 'Short to Ground' for engine oil temperature when the fault is active.
- Inspect the sensor connector and engine harness connector for corrosion, moisture, bent pins, or pushed-back terminals. Look closely at the seals for damage or misalignment.
- Trace the harness from the sensor back toward the ECM, checking for chafed, pinched, or shorted wiring, especially anywhere the harness rubs against engine components.
- With the connector disconnected, check for continuity and correct resistance between terminal 1 (signal) and terminal 2 (common) at the sensor itself to see if the sensor is shorted internally.
- Remember terminal 2 is a shared common line with the coolant, oil (end), and intake manifold air temperature sensors. If more than one temperature-sensor code is active, focus first on the shared common wiring.
- If wiring and connectors check good and the sensor tests bad, replace the engine oil temperature sensor and recheck for the code.
- If the sensor and harness both check good, suspect the ECM as a last step.
How the code clears
No separate clearing step is listed. Once the underlying wiring, connector, or sensor problem is repaired, verify the fix by watching the live oil temperature status on a display module or Cat ET. Clear the logged code with the diagnostic scan tool and confirm it does not return after a normal warm-up and shutdown cycle.
Affected models and serial ranges
1754 appears in our records across 5 CAT Engine models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| C13 | Serial range not listed in source records |
| C15 | 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 |
Frequently asked questions
What does CAT code 1754 mean?
It means the ECM detected the signal from the engine oil temperature sensor (middle) reading below 0.2 volts for at least eight seconds, which the ECM interprets as a short to ground in that sensor circuit.
Is CAT fault 1754 the same as SPN 175 FMI 4?
Yes. CID 175, FMI 04 on the Cat Data Link corresponds to SPN 175, FMI 4 on the J1939 data link, and this same fault also triggers flash code 37 on the diagnostic lamp.
Will the engine still run with code 1754 active?
Yes. The ECM substitutes the coolant temperature reading in place of the invalid oil temperature signal. If the coolant sensor has also failed, it uses a fixed default of 65 °C (149 °F) while running or -10 °C (14 °F) when the engine is off.
What symptoms come with this code?
Hard starting, rough idle, and excessive white smoke are the symptoms tied to this fault.
Why does the shared sensor common wire matter for this code?
Terminal 2 on the oil temperature sensor connects to a common ground line shared by the coolant, oil (end), and intake manifold air temperature sensors. A fault on that shared line can cause multiple temperature-sensor codes to appear at once, so checking that common wiring first can save diagnostic time.
Do I need to replace the ECM to fix code 1754?
Rarely. Faulty connectors, damaged wiring, out-of-place seals, or a failed sensor are far more common causes. The ECM is listed as a possible cause only after wiring and the sensor have been ruled out.