Damaged wiring, poor connector contact or corrosion in the tank temperature sensor circuit; Faulty tank temperature sensor; Loss of communication or invalid data between the tank monitoring module and the module that sets the code; Low or unstable supply voltage, or a poor earth, affecting the sensor or module; Fault inside the tank or fuel system control module; Outdated module software where the manufacturer has issued a bulletin for this fault.

U354A

Hydrogen Tank A Temperature Sensor 1 Circuit.

Generic
Network
Generic code
Medium severity

How this code is built

U: SystemNetwork
3: Defined bySAE, the same on every car
5: AreaNetwork area 5
4A: FaultThe specific fault in that area

What it means

U354A is defined here as a fault in the Hydrogen Tank A Temperature Sensor 1 circuit. It is a network-range code, so a control unit has either lost a valid temperature signal from that sensor or is receiving data from it that it cannot trust. The exact trigger, such as an open circuit, a short, or invalid data from another module, depends on the vehicle and which module sets the code. Only a few models use hydrogen storage, so use the manufacturer's information for the details.

Symptoms

Fuel system or fuel cell warning light on the dashboard
Refuelling refused, limited or reported as unavailable
Reduced power or the vehicle entering a limited operation mode
Inaccurate or missing hydrogen tank temperature or range information
Other communication fault codes stored alongside it

Possible causes

Damaged wiring, poor connector contact or corrosion in the tank temperature sensor circuitlikely
Faulty tank temperature sensorlikely
Loss of communication or invalid data between the tank monitoring module and the module that sets the codepossible
Low or unstable supply voltage, or a poor earth, affecting the sensor or modulepossible
Fault inside the tank or fuel system control modulerare
Outdated module software where the manufacturer has issued a bulletin for this faultrare

How to diagnose

Read all stored and pending codes and note the freeze frame data. Look for other network, voltage or hydrogen system codes that point to a common cause.
Check the manufacturer's information for this model to find out which module sets U354A and how the sensor circuit is arranged.
Look for any warnings, odours or leak indications. Do not carry out any work on the hydrogen system unless you are trained and equipped for it.
Inspect the sensor wiring and connectors for chafing, water ingress, corrosion, bent pins or loose fit, without disturbing any hydrogen or high voltage components.
Check battery condition and the low voltage supply and earth connections to the relevant modules.
With the sensor live data, check that the temperature reading is plausible and does not jump, freeze or drop out when the harness is gently moved.
Test the circuit for continuity, short to earth and short to supply, following the manufacturer's wiring diagram and safe isolation procedure.
Check for software updates or technical bulletins for the module concerned before replacing it.

How to fix

Repair or replace damaged wiring and clean or renew faulty connectors in the sensor circuit.
Replace the tank temperature sensor if it fails testing, using a trained technician and the manufacturer's procedure for the hydrogen system.
Correct any low voltage supply or earth fault affecting the modules.
Repair any communication fault found on the network between the modules involved.
Replace or reprogram the control module only if testing proves it faulty or the manufacturer lists a software update for this fault, then clear the code and confirm it does not return.

Can I keep driving?

Medium severity

Treat any fault in a hydrogen storage system with caution and have it checked soon, as the car may restrict power or refuelling. If you see a hydrogen system warning, notice any odour or leak, or the vehicle goes into limited operation, stop safely and seek specialist help.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.