What does it mean?
Unlike a hard low or high fault, this code is set by a tank A pressure signal that is present but unstable. The fuel system control module continuously watches the rate of change of the CNG or LPG tank pressure value and knows that real tank pressure moves slowly, following temperature and consumption rather than jumping. When the signal drops out momentarily, spikes, or changes faster than any physical tank behaviour allows, the module flags the circuit as intermittent or erratic. Faults like this are usually mechanical damage to the connection rather than a failed component, and they very often correlate with rough roads, vibration, temperature swings or washing the vehicle. Because the sensor lives under the vehicle in the weather, corrosion and chafing dominate the cause list.
Symptoms
- MIL (check engine lamp) that comes and goes, often on rough surfaces
- Gas fuel gauge needle jumps, drops to empty and then recovers
- Sudden unrequested switch from gas to gasoline, followed by normal operation afterwards
- Refill detection triggers when no fuel has been added
- The fault may reappear only after driving over bumps or in wet weather
Likely causes
- Loose, corroded or partially backed-out terminals in the tank sensor connector
- Chafed insulation on the underbody harness that touches ground only when the loom moves
- Water inside the connector body that bridges pins intermittently and dries out again
- Cracked solder joint or a failing element inside the pressure sensor
- Poor or corroded sensor ground point that opens up under vibration
- Signal wire routed against a high-current cable or the ignition system, picking up electrical noise
- Loose connector at the control module end of the circuit
How to fix it
- Read the freeze frame to learn what speed, load and temperature were present when the code set, which narrows down where to wiggle test
- Graph the tank pressure value on a scan tool while wiggling the harness and connector at the tank; a dropout while moving the loom pinpoints the fault
- Open the sensor connector and check terminal tension with a matching pin; also look for water, salt residue and green corrosion
- Inspect the entire underbody run of the harness for rub-through at brackets, heat shields and the tank straps
- Measure the sensor ground for voltage drop while tapping the loom, and clean or remake any ground stud that shows resistance
- Repair or replace the affected terminals and re-seal the connector, then road test over the conditions in the freeze frame to confirm the signal stays stable
- Replace the pressure sensor only if the signal still drops out with a known good harness attached