FTS stands for Fuel Temperature Sensor. It measures the temperature of the fuel and sends this information to the engine control module (ECM/PCM). The ECM uses fuel temperature data to adjust fuel control and engine operating strategies.
What Is the FTS Fuel Temperature Sensor?
The Fuel Temperature Sensor (FTS) is usually a thermistor that changes its electrical resistance according to fuel temperature. In many vehicles, it is an NTC sensor, meaning resistance decreases as fuel temperature increases.
The ECM supplies a reference voltage to the sensor and monitors the returning signal voltage. From this voltage, the ECM calculates the approximate fuel temperature.
What Does the FTS Sensor Do?
The main function of the FTS is to provide the ECM with accurate fuel temperature information. Fuel temperature can affect fuel density, fuel delivery calculations, emissions control and engine performance.
When fuel temperature changes significantly, the ECM can compensate for the change in fuel characteristics and operating conditions.
Where Is the Fuel Temperature Sensor Located?
The exact location depends on the vehicle and fuel system design.
- Inside the fuel tank.
- Integrated into the fuel pump module.
- Installed in the fuel supply system.
- Located near the fuel rail or fuel injection system on some applications.
- Integrated into another fuel system sensor or module on certain vehicles.
Older vehicles can also use fuel temperature sensing, although the sensor design and location may differ considerably from newer vehicles.
FTS Signal Flow
ECM / PCM | | 5V Reference v FTS Fuel Temperature Sensor | | Variable Signal Voltage v ECM / PCM | v Fuel Temperature Calculation | v Fuel Control / Engine Strategy
The actual circuit can vary by manufacturer. Some systems use a dedicated sensor ground or sensor return circuit rather than a simple two-wire arrangement.
Typical FTS Pinout
Many conventional fuel temperature sensors use a simple two-wire thermistor circuit. A typical arrangement may include:
- Pin 1: Sensor signal / ECM reference circuit
- Pin 2: Sensor ground or signal return
However, the pinout is not universal. Always verify the wiring diagram for the specific vehicle before testing. Some fuel temperature sensors are integrated into larger fuel system assemblies.
Does the FTS Use CAN Bus?
A conventional FTS connected directly to the ECM normally does not have CAN-H and CAN-L wires. The sensor normally communicates with the ECM through its electrical signal circuit.
On some modern vehicles, however, the fuel temperature information may be processed by another control module and transmitted to the ECM through the CAN network.
Common Symptoms of a Bad FTS
- Check Engine Light.
- Incorrect fuel temperature reading in live data.
- Hard starting.
- Rough engine operation.
- Reduced fuel economy.
- Incorrect fuel mixture under certain conditions.
- Engine performance problems.
- Intermittent sensor-related fault codes.
Common Causes of FTS Failure
- Failed thermistor inside the sensor.
- Open circuit in the wiring.
- Short to ground.
- Short to voltage.
- Corroded connector terminals.
- Damaged wiring near the fuel tank.
- Poor sensor ground or signal return.
- Fuel pump module damage when the sensor is integrated into the module.
- ECM/PCM circuit problems.
Common OBD-II Codes Related to Fuel Temperature
Fuel temperature sensor faults are commonly associated with the P0180–P0189 code family. Exact code usage depends on the manufacturer and vehicle.
- P0180: Fuel Temperature Sensor A Circuit
- P0181: Fuel Temperature Sensor A Circuit Range/Performance
- P0182: Fuel Temperature Sensor A Circuit Low
- P0183: Fuel Temperature Sensor A Circuit High
- P0185: Fuel Temperature Sensor B Circuit
- P0186: Fuel Temperature Sensor B Circuit Range/Performance
- P0187: Fuel Temperature Sensor B Circuit Low
- P0188: Fuel Temperature Sensor B Circuit High
- P0189: Fuel Temperature Sensor B Circuit Intermittent
Manufacturer-specific codes may also be used, so the vehicle service information should always be checked before replacing the sensor.
How to Test the FTS With a Scan Tool
Connect a compatible OBD-II scanner and open the live data section. Look for Fuel Temperature, Fuel Temp, or FTS.
With the engine cold, the fuel temperature should normally be reasonably close to the surrounding temperature. As the fuel temperature changes, the scanner reading should change smoothly rather than suddenly jumping to an extreme value.
A reading such as an extremely low or extremely high temperature that does not match actual conditions can indicate a sensor or wiring problem.
FTS Oscilloscope Test
Because many FTS sensors are NTC thermistors, the oscilloscope normally shows a relatively stable DC voltage that changes gradually as fuel temperature changes. It is not normally a repeating waveform like a crankshaft or camshaft sensor.
Normal FTS Signal
Voltage
|
5V|\
| \
| \
| \____
|
+--------------------> Time
Temperature changes
The exact voltage depends on the sensor design, ECM pull-up circuit and fuel temperature. A sudden drop to 0 V, a fixed high voltage, or intermittent signal interruptions can indicate wiring, connector or sensor problems.
Basic FTS Oscilloscope Connections
- Connect the oscilloscope ground to a suitable sensor ground.
- Connect the probe to the FTS signal wire.
- Back-probe the connector without damaging the terminals.
- Monitor the signal while the fuel temperature changes.
- Compare the waveform with the manufacturer's specifications whenever available.
Do not assume the wire colors or pin numbers are the same on every vehicle.
FTS Diagnostic Tips
If the scan tool shows an implausible fuel temperature, do not immediately replace the sensor. Check the connector, wiring, sensor reference circuit and ground first.
If the sensor reading changes when the wiring harness is moved, an intermittent wiring or connector problem may be present.
FTS Replacement Cost
The replacement cost depends heavily on the vehicle design. A separately accessible fuel temperature sensor may be relatively inexpensive, while a sensor integrated into the fuel pump module can make the repair considerably more expensive.
A typical repair can range from approximately $100 to $500 or more, including parts and labor, depending on the vehicle and whether the fuel tank or pump module must be removed.
Can Older Vehicles Have an FTS?
Yes. Fuel temperature sensing is not limited to modern vehicles. Some older fuel injection systems also monitor fuel temperature, although the sensor may be installed differently and may use different terminology or diagnostic procedures.
For older vehicles, always check the factory wiring diagram and service manual because the sensor location and circuit design can differ substantially from newer vehicles.
Common Diagnostic Mistakes
- Replacing the FTS without checking the wiring.
- Assuming every FTS has the same pinout.
- Assuming FTS always communicates through CAN Bus.
- Ignoring the sensor ground or return circuit.
- Replacing the complete fuel pump module before confirming the sensor fault.
- Using generic resistance specifications from another vehicle.
Frequently Asked Questions
What does FTS mean on a scan tool?
FTS commonly means Fuel Temperature Sensor. Some scan tools may display the same parameter as Fuel Temperature or Fuel Temp.
Is FTS the same as a fuel pressure sensor?
No. The FTS measures fuel temperature, while a fuel pressure sensor measures fuel pressure.
Does every FTS have two wires?
No. Many conventional thermistor-type sensors use two wires, but the circuit can vary depending on the vehicle and fuel system design.
Can a bad FTS cause a Check Engine Light?
Yes. An electrical fault, implausible signal or intermittent FTS signal can trigger fuel temperature-related diagnostic trouble codes.
Can I diagnose an FTS with an oscilloscope?
Yes. An oscilloscope can help identify unstable signals, wiring interruptions and abnormal voltage changes, especially when the fault is intermittent.
Conclusion
The FTS Fuel Temperature Sensor is an important part of the fuel management system. It provides the ECM with fuel temperature information that can be used for fuel control and engine operating calculations. When diagnosing an FTS fault, check the live data, wiring, connector, reference circuit, sensor return and signal before replacing the component.
Because fuel temperature sensor designs vary between manufacturers and model years, the correct wiring diagram and factory specifications should always be used for accurate diagnosis.