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U355D Expander Inlet Pressure Sensor 1 Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Wiring or connector of sensor 1 at the wet exhaust side corroded, open or shorted
Expander inlet pressure sensor 1 faulty internally
Sensor supply or ground faulty

Symptoms

  • Fuel cell system warning, MIL on
  • Higher hydrogen consumption because less energy is recovered
  • Reduced peak power

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–800
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

expander inlet pressure sensor 1sensor wiring

Related codes

U355EU355FU3560U3559

References: garrettmotion.com, patents.google.com, static.nhtsa.gov.