Circuit Description
WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The fuel rail temperature (FRT) sensor is a variable resistor that measures the temperature of the fuel in the compressed natural gas (CNG) fuel rail. The fuel injector control module (FICM) supplies 5 volts to the FRT signal circuit and supplies a ground to the low reference circuit. The FICM monitors the FRT sensor voltage and communicates the data to the powertrain control module (PCM) by a dedicated pulse width modulated (PWM) circuit. This DTC sets when the FRT temperature is not near the expected temperature.