U355D code meaning
Expander Inlet Pressure Sensor 1 Circuit
Network system Generic code U35xx codes Check engine light
What U355D means
U355D covers the first pressure sensor in front of the expander, a turbine in the cathode exhaust that turns leftover pressure from the stack outlet into shaft power for the compressor. Garrett states that its optional turbine expander, developed among others for the compressor of the BMW iX5 Hydrogen, lowers the electricity needed for compression by up to 20 %. In a Toyota patent a waste gate valve divides exhaust between turbine and bypass, because the flow resistance of the turbine raises the pressure the compressor must supply and can push it toward surge. A sensor at the turbine inlet shows this back pressure directly. No maker documents U355D. Losing it takes an input from energy recovery and cathode pressure control. Toyota's Mirai bulletin T-SB-0043-23 shows that faults on the cathode air side light the MIL.
U355D at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U355D
- Fuel cell system warning, MIL on
- Higher hydrogen consumption because less energy is recovered
- Reduced peak power
Common causes of U355D
- Most likelyWiring or connector of sensor 1 at the wet exhaust side corroded, open or shorted
- PossibleExpander inlet pressure sensor 1 faulty internally
- Less likelySensor supply or ground faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Expander inlet pressure sensor 1Sensor wiring
What each part of U355D means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 5D | The exact fault in that area. |
What to do next
- Note U355D 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 U355D
What does U355D mean?
U355D means "Expander Inlet Pressure Sensor 1 Circuit". U355D covers the first pressure sensor in front of the expander, a turbine in the cathode exhaust that turns leftover pressure from the stack outlet into shaft power for the compressor. It is a generic code, so it means the same on every make.
Is it safe to drive with U355D?
Drive gently and only to a workshop. With U355D the car can go into limp mode (reduced power) to protect itself.
Will U355D fail an emissions test?
U355D 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 U355D to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U355D clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.