U0677 code meaning
Lost Communication With Fuel Level Sensor B
Network system Generic code U06xx codes Check engine light
What U0677 means
A second level sender is needed when a tank has two chambers, as in saddle tanks that straddle the driveshaft, or when a vehicle carries a second tank. GM's 25OBDG03B calls it sensor 2 of the secondary tank, used on vehicles with two senders and a mechanical transfer pump; its circuit checks fail below 10 % or above 60 % of the 5 V range in 40 of 50 samples (P2067/P2068, Type B). Ford's 2024 summary runs sender B through the same resistance, noise and stuck checks as A and adds P25B2 for a stuck reading on either. U0677 is the digital variant: sender B's messages stop arriving. No manufacturer documents it publicly. The gauge then misjudges the part of the tank sender B covers, and range and EVAP readiness suffer.
U0677 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0677
- Gauge drops suddenly or never shows full
- Range estimate inaccurate
- Check engine light
Common causes of U0677
- Most likelyWiring to the secondary-chamber sender damaged
- PossibleSender B electronics failed
- PossibleConnector at the secondary flange corroded
- Less likelyReceiving module or software faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel level sensor bVehicle bus wiring
What each part of U0677 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 77 | The exact fault in that area. |
What to do next
- Note U0677 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0677
What does U0677 mean?
U0677 means "Lost Communication With Fuel Level Sensor B". A second level sender is needed when a tank has two chambers, as in saddle tanks that straddle the driveshaft, or when a vehicle carries a second tank. It is a generic code, so it means the same on every make.
Is it safe to drive with U0677?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will U0677 fail an emissions test?
Yes, it can. U0677 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U0677 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3.5 hours of work. This is a job for a workshop.
Will U0677 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.