CAT Engine 1743 Fault Code: Fuel Temperature open/short to +batt
Also called Engine Fuel Temperature 1 : Voltage Above Normal, Fuel Temperature Open/Short to +Batt, Fuel Temperature Sensor - Votlage Above Normal, Fuel Temperature Sensor : Voltage Above Norma, Fuel Temperature Sensor : Voltage Above Normal, Fuel Temperature Sensor Voltage Above Normal, Fuel Temperature Sensor voltage Above Normal, Fuel Temperature Sensor voltage above normal, Fuel Temperature Sensor: Voltage Above Normal, Fuel Temperature Sensor:Voltage Above Normal, Fuel TemperatureSensor : Voltage Above Normal
Fuel Temperature open/short to +batt · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
CAT code 1743 means the ECM sees fuel temperature sensor signal voltage above 4.8 VDC for one second while the ECM has been powered for at least three seconds. The ECM logs the code, flags fuel temperature as invalid, and substitutes a default value (either 30 °C (86 °F) or 40 °C (104 °F) depending on the OEM text version) so the engine keeps running on a fake reading instead of real data.
Medium severity. This code does not stop the engine, but it puts the ECM into a low power state and runs on a default fuel temperature value instead of real sensor data. Left unresolved it can affect fueling accuracy and performance, so it should be diagnosed within the shift rather than ignored long term.
What does CAT Engine error code 1743 mean?
Code 1743 covers the engine fuel temperature sensor circuit. This sensor tells the ECM how hot the fuel is so the ECM can adjust fuel delivery calculations for accurate power and emissions control. When the ECM sees a signal voltage that is higher than it should ever be for a working sensor, above 4.8 VDC for one second, it decides the reading is not trustworthy.
Once that condition is confirmed, with the ECM having been powered for at least three seconds, the ECM logs the fault and stops using the live signal. Instead it substitutes a fixed default temperature so the engine control strategy has something to work with. Different versions of this CAT diagnostic text list the default as 30 °C (86 °F) or 40 °C (104 °F), so the exact fallback value can vary by engine family or software revision.
The practical effect described is 'low power', meaning the engine may run in a reduced performance mode while this code is active, since the ECM is not confident in actual fuel temperature and is protecting the engine and fuel system by backing off.
Common causes of 1743
- Connectors, pins, or sockets at the sensor or ECM that are not fully coupled or inserted
- Corrosion, abrasion, or pinch points in the harness and wiring
- An open or short circuit in the sensor circuit
- A short between the signal wire and ground
- A short between the analog sensor common and the signal wire
- An open circuit in the 5 volt supply wire feeding the sensor
- A short between the 5 volt supply and the signal wire
- A faulty or degraded fuel temperature sensor that needs replacement
- A faulty ECM (listed as a possible cause across multiple versions of this diagnostic)
- Damaged connectors
- An intermittent wiring or connection problem
How to troubleshoot CAT Engine 1743: first checks
- Inspect the fuel temperature sensor connector and the mating ECM connector to confirm they are fully seated and locked, not just partially plugged in
- Visually trace the harness for corrosion, chafing, or pinch points, especially where it runs near moving parts or sharp edges
- With the key off, check the signal wire for a short to ground and check for a short between the signal wire and the 5 volt supply wire
- Verify the 5 volt supply wire to the sensor has continuity and is not open circuit
- Check terminal 1 (signal) and terminal 2 (sensor return) at the sensor connector for correct wiring per the passive analog sensor circuit design
- Test the sensor itself against its expected resistance or voltage behavior and swap with a known good sensor if available
- Wiggle-test the harness and connectors while watching for the fault to reappear intermittently, since intermittent connection problems are a listed cause
How the code clears
No separate clearing step is listed beyond fixing the root cause. Once the wiring, connector, or sensor issue is repaired and the ECM reads a normal in-range signal voltage, the code should stop being active. Note that the ECM performs an automatic calibration of these sensors whenever it is powered with the engine off for at least five seconds, so leaving the key on with the engine off for that duration after a repair may help the ECM recheck the circuit.
Affected models and serial ranges
1743 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 1743 mean?
It means the ECM detected fuel temperature sensor signal voltage above 4.8 VDC for one second, which is outside the normal operating range for that sensor circuit. The ECM treats the reading as invalid and substitutes a default temperature value instead.
Will code 1743 shut down my CAT engine?
No shutdown is listed. The documented system response is that the ECM logs the code, uses a default fuel temperature value, and the engine may enter a low power state rather than stopping.
What default fuel temperature value does the ECM use with this code active?
Depending on the specific version of the diagnostic text for your engine, the ECM substitutes either 30 °C (86 °F) or 40 °C (104 °F) in place of the real sensor reading.
What are the most common causes of fault 1743?
The most frequently listed causes are damaged or loose connectors, harness wiring problems such as corrosion or a short to ground or to the 5 volt supply, a faulty fuel temperature sensor, and in some cases a faulty ECM.
Which engines can set code 1743?
This code is documented across the C10, C11, C12, C13, C15, C16, C175, C18, C27, and C32 CAT engine families.
How do I know if it is the sensor or the wiring causing this code?
Check the connectors and wiring first for looseness, corrosion, and shorts to ground or to the 5 volt supply line, since those are listed as common causes. If wiring and connectors check out and the fault persists, replace the sensor. If the fault still returns after that, ECM failure is listed as a possible but less common cause.
Is there a special reset procedure for code 1743?
No separate clearing step is listed for this code. Repairing the underlying wiring, connector, or sensor issue so the signal voltage returns to a normal range should allow the code to clear on its own.