U354DHydrogen Tank B Temperature Sensor 2 Circuit
- Generic OBD-II code · Network
- Turns on the check-engine light
- How the car detects it
- U354D marks an electrical fault on the second temperature sensor of tank B. Apart from fill control, tank temperature is needed to convert pressure into fuel quantity, because cold gas at a given pressure holds more hydrogen than warm gas. Sensors and wiring sit at the tank under the floor, often inside the on-tank valve. Hyundai's venting bulletin 20-FL-008H-1 for the Nexo has the underbody covers removed to reach the tank valves, requires tank pressure below 500 psi before work on hydrogen parts and full venting before welding or open flame within 18 inches. A sensor fault on the tank can therefore become a job involving defuelling. No maker publishes U354D. Its partner on the same tank is U354C.
- What you may notice
- Hydrogen system warning
- Fuel gauge less accurate
- Refuelling ends early
- Likely causes
- LikelyMoisture or damage at the underbody connector of tank B
- PossibleTemperature sensor 2 of tank B failed
- RareHarness chafed after underbody or tank work
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €80 – €4,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.