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Home / DTC / U3549 — Hydrogen Tank High Pressure Sensor 1 Circuit

U3549 — Hydrogen Tank High Pressure Sensor 1 Circuit

Detailed page for trouble code U3549.

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22,458specific
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Code

U3549

Generic U — Network/User

Hydrogen Tank High Pressure Sensor 1 Circuit

Brand: Generic
Type: U — Network/User
Views: UK: 12 EN: 20 RU: 22
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Page language: EN

Causes

  • Open or short in sensor signal wiring or connector
  • Corroded, bent or pushed‑out connector pins
  • Hydrogen tank high‑pressure sensor internal failure
  • Blown fuse or faulty power/ground to sensor
  • Poor sensor ground or intermittent connection
  • ECU/PCM module fault or corrupted software

Symptoms

  • Malfunction Indicator Lamp (MIL)/warning light illuminated
  • Hydrogen system warning or reduced system performance message
  • Possible limp‑home mode or restricted vehicle operation
  • Incorrect or no tank pressure reading on dash/integrated display
  • Difficulty starting or no start if system is disabled for safety

What to check

  • Read current and historic freeze‑frame data and full DTC list with a capable scan tool
  • Inspect harness and connectors at the hydrogen tank sensor and along routing for chafing, heat damage or corrosion
  • Inspect and verify fuses, relays and sensor supply/ground at the ECM/modular control unit
  • Backprobe sensor connector and measure reference supply voltage, ground continuity and signal voltage with ignition ON (follow safety procedures)
  • Wiggle test harness while monitoring live data for intermittent changes
  • Check for related hydrogen system codes and module communication errors

Signal parameters

  • Reference/Excitation: typically 5.0 V (verify with service data)
  • Ground: near 0 V, low resistance to chassis ground
  • Signal output: nominally ~0.5–4.5 V proportional to pressure (manufacturer specific)
  • If sensor is resistive type: resistance varies smoothly with pressure (service data required)
  • Signal should change smoothly as pressure is varied; no sudden steps or dropouts

Diagnostic algorithm

  1. Retrieve code(s), freeze frame and live data; note any related hydrogen system or communication codes.
  2. Follow manufacturer safety procedures: isolate and depressurize hydrogen system before performing work near the tank or fittings.
  3. Visually inspect sensor, connector and harness for damage, corrosion, water ingress or rodent damage.
  4. Check power and ground at the sensor connector with ignition ON: verify correct reference voltage and a good ground (compare to chassis ground resistance).
  5. Backprobe the signal terminal and observe voltage while a second person changes tank pressure (or use vehicle self‑test) — signal should vary smoothly and be within spec.
  6. Check continuity of signal, power and ground wires between sensor and control module; look for short to battery or ground.
  7. If wiring and connectors are good but signal out of specification, substitute a known‑good sensor or measure sensor resistance per service data; replace sensor if out of spec.
  8. If symptoms persist after sensor replacement, inspect module connector pins and test module outputs; reprogram or replace control module only after confirming wiring and sensor faults are cleared.
  9. Clear codes and perform functional test/road test; monitor live data to confirm correct operation.

Likely causes

  • Damaged/chafed harness at tank or through body harness
  • Connector corrosion at the tank (water ingress)
  • Internal sensor element failure due to age/contamination
  • Short to battery or to ground on the signal wire
  • Loose or corroded ground or reference supply at control module

Fault status

⚠️ Status
U3549 — Hydrogen Tank High Pressure Sensor 1 Circuit: signal open/short/out of range detected
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

P0193 P0192 P0108 P0106 U0121 U0100
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