U0670 code meaning
Lost Communication With Fuel Temperature Sensor A
Network system Generic code U06xx codes Check engine light
What U0670 means
GM's 2025 direct-injection engines measure fuel temperature in the high-pressure rail with digital SENT sensors, and sensor 1 is the one GM files under U0670. The test counts pulses on the signal wire: if the line sits permanently high and four or fewer pulses arrive (25OBDG03A; 40 or fewer in 25OBDG03B), a sample fails, and 400 bad samples in a window of 500, one every 6.25 ms, set the code; being Type A, it lights the MIL during the first trip. While it is active, GM holds back the range checks P0182/P0183 and the sensor comparison P111F. CARB requires a separate code when a digital input stops talking. The controller then substitutes a fuel temperature, so drivability rarely changes; the fault lies in wiring, connector or sensor.
U0670 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0670
- Check engine light from the first trip
- Usually no noticeable change in driving
- Occasionally rougher hot restarts
Common causes of U0670
- Most likelySENT signal wire to sensor A shorted or open
- PossibleConnector at the fuel rail loose or contaminated
- PossibleFuel temperature sensor A internally failed
- Less likelySENT receiver in the engine controller faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel temp sensor aVehicle bus wiring
What each part of U0670 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 70 | The exact fault in that area. |
What to do next
- Note U0670 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 U0670
What does U0670 mean?
U0670 means "Lost Communication With Fuel Temperature Sensor A". GM's 2025 direct-injection engines measure fuel temperature in the high-pressure rail with digital SENT sensors, and sensor 1 is the one GM files under U0670. It is a generic code, so it means the same on every make.
Is it safe to drive with U0670?
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 U0670 fail an emissions test?
Yes, it can. U0670 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 U0670 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will U0670 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.