Network, generic (extended)

U354E Hydrogen Tank C Temperature Sensor 1 Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U354E points to an electrical fault on sensor 1 of tank C, a tank that exists only on three-tank vehicles: the second-generation Mirai, whose long central tank is joined by two smaller ones crosswise under the rear seat and the boot, or the Nexo with three tanks holding 156 litres. On a two-tank car such as the first Mirai or the Clarity the code would suggest a configuration or software mismatch. The sensor is not the overheat protection: a thermally activated relief device opens on its own, on Toyota's FCHV at 110 °C, without electronics. A lost sensor costs information, not the fire safeguard. No manufacturer documents U354E publicly; sensor 2 of tank C is U354F.

Likely causes

Wiring or connector fault at tank C
Temperature sensor 1 of tank C failed
Controller coded for a different number of tanks

Symptoms

  • Hydrogen system warning
  • Refuelling slower or stopped early

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€50–4,000
Time0.3–6 h

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

Parts involved

h2 tank c temp sensor 1sensor wiring

Related codes

U354FU354AU354C

References: newsroom.toyota.eu, en.wikipedia.org, techinfo.toyota.com.