What does it mean?
Rather than a permanent circuit failure, this code records a gaseous fuel rail temperature signal that is unstable over time. Thermal mass in the rail and the sensor tip means the reading should change gradually, so a value that jumps tens of degrees between samples or briefly disappears cannot be a real measurement. The module logs the circuit as intermittent or erratic once these dropouts occur often enough within a monitoring window. Because the sensor lives on the engine in a hot, vibrating, heat-cycled environment, the usual culprits are fretted terminals, brittle insulation and grounds that open under vibration. The driver may experience a stumble or an unexpected changeover, and the code often clears itself only to return days later.
Symptoms
- MIL (check engine lamp) that comes on and clears without repair
- Rail temperature value that spikes or drops momentarily on a scan tool
- Occasional stumble, hesitation or brief misfire while running on gas
- Unexpected changeover from gas back to gasoline during a drive
- Symptoms that appear on rough roads or once the engine is fully hot
- Nothing reproducible when the engine is idling cold in the workshop
Likely causes
- Loose or fretted terminals in the rail temperature sensor connector
- Heat-embrittled insulation that cracks and touches ground when the harness moves
- Chafed signal wire against a bracket, hose clamp or the engine itself
- Intermittent open inside the thermistor, typically appearing as the sensor heats up
- Corroded or loose ground point that opens under vibration
- Signal wire routed close to ignition components and picking up electrical noise
- Loose connector at the gaseous fuel control module
How to fix it
- Read the freeze frame to identify the temperature, load and speed at which the code set
- Graph the rail temperature signal while wiggling the connector and the harness, and while heating the suspect area gently with the engine running
- Check terminal tension in the sensor connector with a matching pin and inspect the contact faces for fretting
- Follow the harness looking for rub points at brackets, hoses, heat shields and anywhere it crosses a moving part
- Voltage drop test the ground circuit while the engine is warm and vibrating rather than at rest
- Repair the terminal, wire or ground, secure and heat-protect the loom, then road test to confirm the trace stays smooth
- Replace the rail temperature sensor when the harness is proven good and the dropouts continue, particularly if they only occur when hot