U3549 code meaning
Hydrogen Tank High Pressure Sensor 1 Circuit
Network system Generic code U35xx codes Check engine light
What U3549 means
U3549 covers the electrical circuit of the high-pressure sensor that reads hydrogen pressure on the storage side, upstream of the regulator, where a full system holds up to 70 MPa, the ceiling set by FMVSS 308. Its value feeds the fuel gauge, fill logic and leak checks: a Hyundai patent watches it while the parked car briefly wakes, a GM patent trims it against the more precise low-pressure sensor whenever the regulator stands wide open, and Toyota compares the filling-side and supply-side sensors after refuelling. U3549 itself appears in no public manufacturer document. An open, a short or a signal outside its range leaves the gauge and leak monitoring blind; expect a warning and possibly limited power. The supply-line sensors have their own codes, U3564 and U3565.
U3549 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U3549
- Hydrogen system warning in the instrument cluster
- Fuel gauge or range display missing or implausible
- Fuel cell power limited
Common causes of U3549
- Most likelyCorroded or damaged connector or wiring between sensor and storage controller
- PossibleHigh-pressure sensor faulty internally
- Less likelySensor supply voltage or ground missing
- Less likelyHydrogen storage control unit faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
H2 tank pressure sensor 1Sensor wiring
What each part of U3549 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 49 | The exact fault in that area. |
What to do next
- Note U3549 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 U3549
What does U3549 mean?
U3549 means "Hydrogen Tank High Pressure Sensor 1 Circuit". U3549 covers the electrical circuit of the high-pressure sensor that reads hydrogen pressure on the storage side, upstream of the regulator, where a full system holds up to 70 MPa, the ceiling set by FMVSS 308. It is a generic code, so it means the same on every make.
Is it safe to drive with U3549?
Drive gently and only to a workshop. With U3549 the car can go into limp mode (reduced power) to protect itself.
Will U3549 fail an emissions test?
U3549 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U3549 to fix?
Difficulty: workshop only. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will U3549 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.