U354AHydrogen Tank A Temperature Sensor 1 Circuit
- Generic OBD-II code · Network
- Turns on the check-engine light
- How the car detects it
- U354A reports an electrical fault on the first temperature sensor of hydrogen tank A. Tank sensors matter most while refuelling: compression heats the gas, and FMVSS 308 slows the pressure ramp once the gas inside passes 85 °C; on the Mirai the tank temperature is passed to the dispenser by infrared. No maker publishes U354A, but Honda shows how such faults appear on the 2017 Clarity Fuel Cell under its own codes P1F76 (main tank) and P1F77 (sub tank): they set during fuelling, and because the sensor sits inside the tank, the first remedy in Tech Line article ATS 170903 was a new tank. Bulletin 19-001 later blamed many cases on outdated software in the fuel cell communication unit. Sensor 2 of the same tank is U354B.
- What you may notice
- Code sets while refuelling
- Hydrogen system warning
- Refuelling slower or ends before the tank is full
- Likely causes
- PossibleOutdated software in the unit that evaluates the tank sensors
- PossibleTemperature sensor inside the tank failed (often only as tank assembly)
- PossibleOpen or short in the sensor wiring or connector at the tank
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €50 – €4,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.