U354E code meaning
Hydrogen Tank C Temperature Sensor 1 Circuit
Network system Generic code U35xx codes Check engine light
What U354E means
U354E points to an electrical fault on sensor 1 of tank C, a tank that exists only on three-tank vehicles: the second-generation Mirai, whose long central tank is joined by two smaller ones crosswise under the rear seat and the trunk, or the Nexo with three tanks holding 156 litres. On a two-tank car such as the first Mirai or the Clarity the code would suggest a configuration or software mismatch. The sensor is not the overheat protection: a thermally activated relief device opens on its own, on Toyota's FCHV at 110 °C, without electronics. A lost sensor costs information, not the fire safeguard. No manufacturer documents U354E publicly; sensor 2 of tank C is U354F.
U354E at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor0.3 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U354E
- Hydrogen system warning
- Refuelling slower or stopped early
Common causes of U354E
- Most likelyWiring or connector fault at tank C
- PossibleTemperature sensor 1 of tank C failed
- Less likelyController coded for a different number of tanks
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
H2 tank c temp sensor 1Sensor wiring
What each part of U354E means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 4E | The exact fault in that area. |
What to do next
- Note U354E and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U354E
What does U354E mean?
U354E means "Hydrogen Tank C Temperature Sensor 1 Circuit". U354E points to an electrical fault on sensor 1 of tank C, a tank that exists only on three-tank vehicles: the second-generation Mirai, whose long central tank is joined by two smaller ones crosswise under the rear seat and the trunk, or the Nexo with three tanks holding 156 litres. It is a generic code, so it means the same on every make.
Is it safe to drive with U354E?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will U354E fail an emissions test?
U354E is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U354E to fix?
Difficulty: workshop only. A typical repair takes 0.3 to 6 hours of work. This is a job for a workshop.
Will U354E clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.