Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Fuel Tank Temperature Sensor
The Tank Temperature (FTT) sensor is a thermistor mounted inside the HPL and is not serviceable separately from the HPL. The FTT thermistor has high resistance when cold and low resistance when hot. The PCM supplies about 5 volts to the FTT sensor signal circuit. When the FTT sensor is cold its resistance is high and the signal voltage is high. As the FTT sensor warms and resistance drops, less signal voltage is monitored by the FICM. The FTT sensor voltage is sent to the PCM through a Pulse Width Modulated (PWM) circuit. The volume of CNG will vary with temperature and pressure. Accurate CNG fuel level cannot be determined by pressure only. To compensate for the different volume factors the FTT sensor is mounted within the HPL. The PCM performs a calculation on the fuel tank pressure vs. the in-tank temperature. The PCM will then display the temperature corrected fuel level.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.