Faulty temperature sensor 1 on hydrogen tank B, such as an open or shorted internal element; Damaged or corroded wiring harness between the sensor and the control module; Loose, corroded, or disconnected electrical connector at the sensor or module; High resistance or open circuit in the sensor ground or signal return path; Failed control module or internal driver circuit for the sensor; Extreme environmental conditions causing sensor degradation, such as prolonged exposure to high heat or vibration; Aftermarket accessories or improper repairs that disturbed the sensor circuit

DTC codes / U35xx · Network communication / U354C

U354CHydrogen Tank B Temperature Sensor 1 Circuit

Q: What does code U354C mean?

Hydrogen Tank B Temperature Sensor 1 Circuit. This code indicates that the powertrain control module has detected an abnormal condition in the temperature sensor circuit for hydrogen tank B, specifically sensor 1. The computer monitors the sensor's signal voltage and flags the code when the reading falls outside the expected range or behaves erratically, pointing to a fault in the sensor, its wiring, or the control module's interpretation of the circuit.

This code indicates that the powertrain control module has detected an abnormal condition in the temperature sensor circuit for hydrogen tank B, specifically sensor 1. The computer monitors the sensor's signal voltage and flags the code when the reading falls outside the expected range or behaves erratically, pointing to a fault in the sensor, its wiring, or the control module's interpretation of the circuit.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaNetwork communication

Symptoms you may notice

Illumination of the malfunction indicator lamp on the dashboard
Often no symptoms besides the warning light, especially if the vehicle continues to operate normally
Reduced fuel cell system performance or power output in some cases
Inability to refuel the hydrogen tank or automatic shutdown of the refueling process
Inaccurate temperature readings displayed on the instrument cluster or energy monitor
Possible limp-home mode or reduced acceleration if the fault affects overall system safety

Common causes, most likely first

Faulty temperature sensor 1 on hydrogen tank B, such as an open or shorted internal element
Damaged or corroded wiring harness between the sensor and the control module
Loose, corroded, or disconnected electrical connector at the sensor or module
High resistance or open circuit in the sensor ground or signal return path
Failed control module or internal driver circuit for the sensor
Extreme environmental conditions causing sensor degradation, such as prolonged exposure to high heat or vibration
Aftermarket accessories or improper repairs that disturbed the sensor circuit

How to diagnose and fix it

Verify the code with a scan tool and check for any related codes in the hydrogen system
Visually inspect the sensor, connector, and wiring for obvious damage, corrosion, or loose connections
Measure the sensor's resistance or voltage output with a multimeter and compare to specifications
Check the wiring continuity and resistance between the sensor and the control module
Test the sensor signal circuit for shorts to ground or power
If the sensor tests out of range, replace the temperature sensor and clear the code
If the wiring and sensor are good, diagnose the control module and repair or replace as needed

Hydrogen sensor circuit quirks to check first

A common oversight is assuming the sensor itself is faulty when the real problem is a chafed wire in the harness near the tank, often caused by vibration or road debris.
The code can be set by a temporary condition such as a loose connector after service, so always check for recent repairs before condemning parts.
Some vehicles use a shared reference voltage for multiple sensors, so a fault in another sensor on the same circuit can trigger this code as well.
The control module may set this code if the sensor signal is plausible but stuck within a narrow range, which can be missed by simple resistance checks.
Do not overlook the sensor ground circuit; a poor ground can cause erratic readings that mimic a failed sensor but are fixed by cleaning the ground point.

Can I keep driving with U354C?

It is generally safe to continue driving if the vehicle operates normally and no other warnings appear, but avoid aggressive driving or long trips until the fault is repaired. If the vehicle enters limp mode or shows reduced power, have it inspected promptly to prevent potential safety issues.

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.