What does it mean?
This code is a plausibility check, not a wiring check. The gaseous fuel module compares the tank temperature reading against other temperature sources it trusts, typically intake air temperature, ambient temperature and engine coolant temperature, usually after a long soak when every sensor on the vehicle should agree closely. It also watches whether the value moves as expected during refuelling and during a long drive.
If the tank temperature stays stuck, responds far too slowly, or is offset by more than the allowed number of degrees from the reference sensors, the module decides the reading is not usable even though its voltage is inside range. The practical effect is a fuel quantity calculation that is skewed, so the gauge and range display become unreliable long before any driveability complaint appears.
Symptoms
- MIL (check engine lamp) on with a gas system rationality fault stored
- Gas gauge and remaining range that clearly do not match how much fuel was put in
- Gauge that drops or rises unexpectedly with weather changes
- Refill event not recognised, so the gauge does not reset after filling
- Cold weather changeover to gas taking longer than usual
- Little or no change in the way the engine actually runs
Likely causes
- Aged or drifted thermistor reading a constant offset from true temperature
- High resistance in the signal or ground circuit caused by corroded terminals, shifting the calculated temperature
- Sensor not properly seated in its port, so it measures air rather than tank or gas temperature
- Wrong or non-matching sensor fitted during a previous repair, with the wrong resistance curve
- Slow response caused by contamination or oily deposits around the sensor tip
- A reference sensor used in the comparison being itself faulty, which the scan tool data will reveal
- Software calibration mismatch after a module replacement
How to fix it
- After an overnight soak, read tank temperature, intake air temperature and coolant temperature together; on a cold vehicle they should be close, and the outlier is the suspect
- Check whether other temperature codes are stored, since a faulty reference sensor can trigger this comparison
- Measure the sensor resistance at a known temperature and compare it with the specification, which exposes a drifted or incorrect part
- Perform voltage drop tests on the signal and ground wires; corroded terminals can shift the reading by several degrees without setting a circuit code
- Verify the sensor is fully seated and correctly torqued in its port, with the right sealing arrangement
- Confirm the correct part number is fitted, especially on a vehicle with a converted or repaired gas system
- Replace the tank temperature sensor when its resistance is out of specification and the wiring has tested good