Network, generic (extended)

U3554 Hydrogen Tank B Valve Enable Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3554 refers to the enable path that powers the tank B solenoid. Its purpose is a second, independent way to withdraw the permission for the valve to open. Toyota patented a layout in which the valve controller and the controller for high voltage sit at opposite ends of the car and back each other up: after a crash at one end, the controller at the undamaged end shuts the hydrogen valve. Toyota's FCHV guide also lists an opened hood or fuel door among the triggers that close the valves. A fault in such a release path keeps tank B shut even with an intact coil. No maker documents U3554 publicly. Check fuses, relays and the release wiring before the valve itself; U3553 covers the control side of the same valve.

Likely causes

Enable relay or switch in the supply path faulty
Open or short in the enable line to valve B
Faulty input that withdraws the release, such as a crash or flap signal

Symptoms

  • Hydrogen system warning
  • Range reduced or no READY

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€50–1,500
Time0.5–4 h

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

Parts involved

h2 tank b valve enablesafety circuit

Related codes

U3553U3555U3551U3557

References: patents.google.com, techinfo.toyota.com.