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U3549 Hydrogen Tank High Pressure Sensor 1 Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Corroded or damaged connector or wiring between sensor and storage controller
High-pressure sensor faulty internally
Sensor supply voltage or ground missing
Hydrogen storage control unit faulty

Symptoms

  • Hydrogen system warning in the instrument cluster
  • Fuel gauge or range display missing or implausible
  • Fuel cell power limited

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–1,500
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

h2 tank pressure sensor 1sensor wiring

Related codes

U3564U3565U3552U0119

References: patents.google.com, patents.google.com, patents.google.com, law.cornell.edu.