Damaged or corroded wiring harness at the hydrogen tank temperature sensor 2 connector; Failed temperature sensor 2 element inside the hydrogen tank assembly; Open or short circuit in the sensor signal or return wire between the tank and the control module; Water or debris intrusion into the sensor connector causing high resistance; Loose or backed-out terminal pins in the sensor or module connector; Internal fault in the control module's sensor input circuit (rare but possible)

DTC codes / U35xx · Network communication / U354B

U354BHydrogen Tank A Temperature Sensor 2 Circuit

Q: What does code U354B mean?

Hydrogen Tank A Temperature Sensor 2 Circuit. U354B is a generic network code indicating that the powertrain control module has lost valid temperature data from the second sensor on the hydrogen tank A circuit. The computer detects an open, short, or implausible signal on the dedicated sensor return circuit, so it flags the fault and may substitute a default temperature value.

U354B is a generic network code indicating that the powertrain control module has lost valid temperature data from the second sensor on the hydrogen tank A circuit. The computer detects an open, short, or implausible signal on the dedicated sensor return circuit, so it flags the fault and may substitute a default temperature value.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaNetwork communication

Symptoms you may notice

Illumination of the malfunction indicator lamp (MIL) with no other noticeable driving issues
Reduced hydrogen injection or power output as the control module limits operation to protect the tank
Incorrect or blank hydrogen tank temperature reading on the dashboard or scan tool data stream
Intermittent warning messages related to the hydrogen system or fuel cell performance
Possible rough running or hesitation if the fault affects mixture calculations during cold starts
Often no symptoms besides the warning light, especially in mild ambient temperatures

Common causes, most likely first

Damaged or corroded wiring harness at the hydrogen tank temperature sensor 2 connector
Failed temperature sensor 2 element inside the hydrogen tank assembly
Open or short circuit in the sensor signal or return wire between the tank and the control module
Water or debris intrusion into the sensor connector causing high resistance
Loose or backed-out terminal pins in the sensor or module connector
Internal fault in the control module's sensor input circuit (rare but possible)

How to diagnose and fix it

Connect a scan tool and record the freeze-frame data for U354B, noting the reported sensor 2 temperature and circuit status
Visually inspect the sensor 2 connector and harness for corrosion, chafing, or loose pins, and repair as needed
Measure resistance across the sensor 2 terminals and compare with the manufacturer's temperature-resistance chart
Back-probe the signal and return wires at the control module connector to check for continuity and short-to-ground
If wiring checks pass, substitute a known-good sensor or simulate the signal with a resistor decade box to confirm the module reading
Replace the faulty temperature sensor 2 or repair the harness section, then clear codes and verify the live data reads correctly
Perform a road test with the scan tool monitoring sensor 2 temperature to confirm the code does not return

Hydrogen tank sensor circuit traps to avoid

A common mistake is replacing the hydrogen tank temperature sensor 2 without first checking the connector for water intrusion, which is a frequent cause on vehicles exposed to road spray.
The code can set intermittently from a harness that rubs against the tank mounting bracket only during certain driving conditions, so a static continuity test may pass.
U354B does not always mean the sensor itself has failed; a poor ground at the control module can skew the return voltage and trigger the same code.
Some vehicles require a relearn or adaptation reset after sensor replacement, and skipping this step will cause the code to reset immediately.
Related codes for the primary temperature sensor or the hydrogen tank pressure sensor often appear alongside U354B, pointing to a shared harness or connector fault.

Can I keep driving with U354B?

You can usually drive the vehicle to a workshop, but avoid heavy loads or long trips because the control module may limit power to protect the hydrogen tank. If the warning light flashes or you notice a strong hydrogen smell, stop safely and have the vehicle towed.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.