Network, generic (extended)

U3550 Hydrogen Tank A Valve Control Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3550 indicates an electrical fault in the control circuit of the solenoid valve on hydrogen tank A. This on-tank valve is the primary closure between tank and fuel system, and FMVSS 308 requires it to default to closed when unpowered. Toyota's FCHV guide lists when the controller shuts the valves of all tanks: vehicle off, abnormal pressure loss or rise, airbag or fuel cell crash sensors, a hydrogen sensor alarm, hood or fuel door opened, or a malfunction of a shut valve. An open coil, a short or a failed driver stage thus leaves tank A closed. No manufacturer documents U3550 publicly. With several tanks the others may keep the car moving with less range; the enable path is U3551, the mechanical function U3552.

Likely causes

Wiring or connector fault between controller and valve
Solenoid coil of the tank A valve open or shorted
Valve driver stage in the storage control unit faulty

Symptoms

  • Hydrogen system warning
  • Reduced range, or no READY if the car depends on this tank

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–5,000
Time1–8 h

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

Parts involved

h2 tank a valvevalve wiring

Related codes

U3551U3552U3553U3556

References: law.cornell.edu, techinfo.toyota.com.