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U3552 Hydrogen Tank A Valve Performance

Check engine lightOn
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

U3552 is the performance code for the valve on tank A: the circuit tests good, but the valve does not act as commanded, either staying shut or failing to seal. With several tanks this is hard to see, because one pressure sensor where the tank lines merge cannot tell that a single tank no longer delivers. Hyundai's answer in a 2018 patent is to estimate how much hydrogen is supplied and compare it with what the stack consumes and purges; another Hyundai patent, with a sensor on each tank, flags the tank whose pressure drifts about 50 bar from the rest. No maker documents U3552 publicly. The driver mainly notices less range and a warning, and the tank with the faulty valve is kept closed. U3555 is tank B.

Likely causes

Tank A valve stuck closed or opening sluggishly
Valve seat no longer sealing
Implausible tank pressure reading misleading the check

Symptoms

  • Noticeably lower range than the gauge suggests
  • Hydrogen system warning

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€500–6,000
Time2–10 h

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

Parts involved

h2 tank a valve

Related codes

U3550U3551U3555U3558

References: patents.google.com, patents.google.com.