OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Network generic or reserved

U3549

Hydrogen Tank High Pressure Sensor 1 Circuit

Generic electrical fault on the high-pressure hydrogen tank pressure sensor 1 (typical operating range up to 700 bar on FCEVs).

SystemNetwork
Typegeneric or reserved
GroupU3
Range / number5 / 49

Possible causes

  • Pressure sensor failed high
  • Gateway module routing CAN messages incorrectly low
  • CAN terminating resistor (120 Ω) drifted out of spec low

Symptoms

  • Multiple warning lights may illuminate
  • Affected modules may go into limp mode or shut down
  • Specific functions inoperative depending on module
  • Diagnostic tools may show communication faults

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 200–2000 €
  • Estimated time: 1–5 h
  • Component: h2 tank pressure sensor 1
  • Component: sensor wiring
  • MIL / check engine light
  • drive cycle required
  • limp mode possible

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication