What does it mean?
This code means the voltage on the alternative fuel tank A level sender circuit has fallen below the lowest value the module will accept as a real reading. A working sender never reaches zero volts even with an empty tank, because its resistance range and the module pull-up circuit always leave an offset at the bottom of the scale. When the signal sits under that floor for a calibrated period, the module treats the level as unknown rather than as an empty tank and stores the code. The most common electrical explanation is a short to ground in the signal circuit or a sender that has shorted internally. The driver loses accurate gas gauge information, and many systems will bring the low fuel warning on as a precaution.
Symptoms
- Gas fuel gauge reading empty regardless of how much gas is in the tank
- Low fuel warning permanently displayed
- MIL (check engine lamp) on with a gaseous fuel system fault stored
- Premature changeover back to gasoline because the module believes the tank is empty
- No range information available for gas operation
- Engine running normally on both fuels apart from the changeover behaviour
Likely causes
- Signal wire shorted to ground along the underbody harness
- Water and corrosion inside the level sender connector bridging the signal to ground
- Sender resistive track shorted internally or the wiper grounded against the tank flange
- Chafed wire where the loom crosses the tank straps, brackets or a heat shield
- Signal wire damaged during a previous tank, multivalve or exhaust repair
- Incorrect sender fitted with a resistance range far below specification
- Module input circuit failure, the least likely cause
How to fix it
- Read the live fuel level value with a known quantity of gas in the tank; a value at zero on a full tank confirms an electrical fault
- Unplug the sender and watch the scan tool. If the reading jumps to full or maximum, the harness is intact and the sender is shorted internally
- If the reading stays at zero with the sender unplugged, the signal wire is shorted to ground and must be traced along the underbody
- Inspect the connector for water, salt, corrosion and pushed-in terminals before any further testing
- Measure the sender resistance at the connector and compare it with the specification for the current level
- Repair the shorted conductor, dry and reseal the connector, then clear the code and verify the gauge responds correctly
- Replace the level sender or multivalve assembly when the wiring measures good and the sender resistance is near zero