Fuel Temp Sensor Circuit Malfunction
The powertrain control module (PCM) has detected an open circuit, short to ground, or short to voltage in the fuel temperature sensor (FTS) #1 signal circuit. This sensor is a thermistor that changes resistance with fuel temperature; the PCM supplies a 5V reference voltage and monitors the voltage drop to calculate fuel temperature. This data is critical for determining fuel density and adjusting the air-fuel mixture, especially during hot/cold starts and evaporative emissions control.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty fuel temperature sensor (internal open or short)
- Open, short to ground, or short to voltage in the signal wire (typically gray/red or similar)
- Corroded, loose, or damaged sensor connector or pushed-out terminals
- Internal PCM failure (rare)
- Fuel contamination altering thermal properties (uncommon but possible)
3. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially hot or cold
- Rough idle or poor fuel economy
- Possible evaporative emissions system fault
4. Step-by-Step Diagnosis
Scan for related codes and freeze frame data
Visually inspect the fuel temperature sensor connector and wiring for damage, corrosion, or loose connections
Measure resistance across the sensor terminals; compare to manufacturer specifications at known fuel temperatures
Check for 5V reference and ground at the sensor connector with the PCM connected
If wiring and sensor check out, test PCM output or perform a PCM reset; replace PCM only if all else fails
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, but you may experience hard starting and reduced fuel economy. The vehicle can be driven short distances, but repair is recommended to avoid potential emissions issues.
How much does it cost to fix?▼
Typically $150 to $350, including parts (sensor $40-$100) and labor (1-2 hours). PCM replacement would be significantly higher.