Code
U354B
Generic
U — Network/User
Hydrogen Tank A Temperature Sensor 2 Circuit
Views:
UK: 25
EN: 34
RU: 26
AI status
Completed
Completed
100%
Causes
- Open or short in sensor wiring (to ground or to battery)
- Corroded, loose, or damaged sensor connector/pins
- Failed temperature sensor (thermistor or sensor module)
- Poor ground or missing reference voltage to the sensor
- Water intrusion or mechanical damage at the tank sensor harness
- Faulty controller/module reading the sensor (ECU/fuel cell controller)
Symptoms
- Malfunction Indicator Lamp (MIL) or hydrogen system warning illuminated
- Hydrogen system derate, disable, or reduced availability of hydrogen functions
- Incorrect or missing temperature value for Hydrogen Tank A Sensor 2 on scan tool
- Stored freeze-frame data showing out-of-range temperature or no signal
- Possible inability to perform hydrogen-related diagnostics or readiness
What to check
- Read and record U354B and any related codes; note freeze-frame and live data
- Verify whether the fault is current or historical and whether it is intermittent
- Visually inspect harness and connectors at Hydrogen Tank A and at the controller
- Backprobe sensor connector and check for reference voltage and ground presence
- Measure sensor resistance/voltage and compare to expected values (sensor spec)
- Wiggle harness and connector while monitoring live data for intermittent change
Signal parameters
- Signal type: temperature sensor (typically NTC thermistor) producing an analog voltage or resistance proportional to temperature
- Typical analog voltage range (typical systems): ~0.1–4.9 V depending on temperature and reference; verify vehicle spec
- Typical resistance behavior: resistance decreases with increasing temperature for NTC sensors — compare to sensor chart in service information
- Expected temperature operating range: manufacturer-specified (examples: -40 °C to +125 °C); check vehicle spec
- Update rate: sensor should update at regular intervals; loss of updates or frozen value indicates a wiring or module issue
- Communication note: some systems transmit processed temperature over CAN — verify both raw sensor circuit and CAN data if applicable
Diagnostic algorithm
- Retrieve and record all related codes and freeze-frame data. Clear codes and attempt to reproduce the fault to verify persistence.
- Visually inspect the hydrogen tank A area, sensor connector, and harness for damage, corrosion, or contamination. Repair any visible issues.
- With ignition ON (engine off) or as directed by service manual, backprobe the sensor connector and measure reference voltage and ground continuity at the controller connector.
- Measure sensor resistance at the sensor plug (or voltage output) and compare to manufacturer temperature vs resistance chart. Warm or cool the sensor gently (heat gun/submerge in temperature-controlled bath per safety procedures) to confirm response.
- Perform continuity checks between the sensor and controller pins to locate opens or shorts; check for short to ground or to battery.
- Wiggle test harness while monitoring live data to find intermittent faults. Inspect routing for chafe points and secure harness if needed.
- If raw sensor circuit checks OK but scan tool shows invalid data, verify CAN/bus communication to the controller and check for related communication codes (U1000, U0401, etc.).
- If wiring and connector tests are good, replace the sensor with a known-good unit and retest. If fault persists after sensor replacement, suspect module/controller fault — consult manufacturer service information before replacing controller.
- After repair, clear codes and verify no return of U354B and that hydrogen system operates normally. Document repair and test drive if applicable.
Likely causes
- Wiring harness chafed where it passes near chassis or other components
- Connector corrosion at the tank or at the controller harness
- Sensor failed due to exposure to moisture or hydrogen environment
- Connector not fully seated after service
- Blown fuse or failed power/ground feed to the sensor circuit
Fault status
Status
Hydrogen Tank A Temperature Sensor 2 Circuit — open, short, invalid or out-of-range signal detected
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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