What it means
Same condition as sensor A stuck, applied to the second fuel level sensor B. Saddle tanks (often AWD vehicles) and large trucks use two sensors — one per tank chamber — averaged for total level. A stuck B leaves only A and reduces accuracy.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Fuel level sensor B reports the level in a second tank chamber or fuel section, commonly in saddle tanks and some large vehicles. P25B1 sets when the module detects that sensor B’s level remains stuck, so the combined tank reading and range estimate may be wrong even if sensor A still responds.
Common causes
Most likely first.
- Fuel level sensor B float stuck or binding
- Faulty sensor B or worn resistive track
- Damaged wiring or connector at sensor B
Symptoms
- Fuel gauge may read inaccurately or change unexpectedly
- Remaining-range estimate may be incorrect
- Check-engine light may come on
How to diagnose it
- Record freeze-frame data and read sensor A and sensor B separately on a scan tool to confirm that B is the reading that remains fixed.
- Compare sensor B data with the fuel gauge and a known change in fuel level, accounting for gauge filtering and update delay.
- Inspect sensor B’s connector and harness for damage, corrosion, loose pins, or poor contact.
- If access is needed, inspect the sensor B float and arm for binding in its tank chamber.
- Test sensor B’s signal across its movement range and check its wiring against the manufacturer's procedure and specification.
Common fixes
- Repair damaged wiring or a poor connection at sensor B.
- Free a binding sensor B float or arm in its tank chamber.
- Replace sensor B if its float or resistive track fails the movement test.
- Correct a damaged connector or terminal that interrupts sensor B’s signal.
Can I keep driving?
You can usually drive if the vehicle operates normally, but the gauge and range estimate may be inaccurate because sensor B’s tank section is not being measured reliably. Refuel early and avoid relying on the gauge alone.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.