What does it mean?
This code covers the same tank A pressure sensor on a CNG or LPG fuel system, but the failure direction is the opposite of a low circuit fault. The sensor is fed a 5-volt reference and returns a signal that climbs with tank pressure, with a defined ceiling that a healthy sensor never exceeds even on a completely full high-pressure tank.
When the fuel system control module sees the signal at or above that ceiling, commonly around 4.8 volts, for a calibrated time, it stores this code and rejects the reading. Electrically, an output stuck at reference voltage almost always means the signal path has lost its connection to the sensor or has picked up voltage from another circuit, rather than an over-pressure condition. The module then substitutes a default fuel level and normally restricts or blocks gas operation.
Symptoms
- MIL (check engine lamp) on and a gaseous fuel fault stored
- Gas fuel gauge shows full regardless of actual tank contents
- Refill detection does not work, so the gauge never updates properly
- Changeover to gas is refused, or the system reverts to gasoline soon after switching
- Fuel range or remaining distance display behaves erratically
- On dedicated gas vehicles, reduced power or a refusal to start
Likely causes
- Open circuit in the signal wire or a disconnected sensor connector, which lets the pull-up voltage float high
- Open sensor ground, so the sensor cannot pull its output down
- Signal wire shorted to the 5-volt reference or short to battery voltage from an adjacent circuit
- Internally failed pressure sensor stuck at maximum output
- Corroded or backed-out terminal in the tank sensor connector creating an open on one pin
- Rodent damage or a pinched loom under the vehicle near the tank
- Fuel system control module input circuit failure, the least common cause
How to fix it
- Read the live tank pressure signal; a value locked at maximum with the engine off and a partly filled tank confirms the circuit fault
- Inspect the sensor connector for pushed-back pins, corrosion or a broken lock that lets the plug sit loose
- Ignition on, back probe the sensor ground at the sensor and confirm it is close to zero volts under load; a floating ground drives the output high
- Jumper the signal pin to ground at the harness connector with the sensor unplugged. If the scan tool value drops to zero, the wiring and module are good and the sensor is at fault
- If the value stays high with the pin grounded, test the signal wire for an open and for a short to reference or battery voltage back to the module
- Repair the open, chafe or short, restore a clean ground, then clear the code and verify the reading changes correctly when the tank is filled
- Replace the tank pressure sensor when the harness checks pass and the sensor output remains pinned high