Network, generic (extended)

U354C Hydrogen Tank B Temperature Sensor 1 Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

U354C flags the circuit of the first temperature sensor in tank B. The maker decides which tank is B, and every series fuel cell car has at least two: the first Mirai carried tanks of 60.0 and 62.4 litres, the Clarity a main and a sub tank. With several tanks the readings can be checked against each other. A Hyundai patent monitors the sensors of three tanks, judges one defective once it sits 20 °C away from the others and replaces its value with a healthy one, so fill control still respects 85 °C and the fuel quantity stays right. Such comparison targets drifting values; an open or shorted sensor as in U354C is recognised directly. No maker documents the code. Sensor 2 of tank B is U354D.

Likely causes

Open or short in the wiring to tank B
Temperature sensor 1 of tank B failed
Input stage of the storage control unit faulty

Symptoms

  • Hydrogen system warning
  • Refuelling limited or interrupted

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 b temp sensor 1sensor wiring

Related codes

U354DU354AU354E

References: patents.google.com, global.toyota, static.nhtsa.gov.