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U355A Charge Air Cooler Outlet Pressure Sensor 1 Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U355A concerns the first of two pressure sensors behind the charge air cooler, where compressed and cooled air heads for the humidifier and the stack. This is the pressure the system really regulates: in a Nissan patent a sensor between intercooler and water recovery unit is the feedback for compressor torque and the outlet pressure valve, and the controller caps this pressure so that compressor and humidifier stay below their heat limits. Toyota takes its counterpart behind compressor and intercooler as the delivery pressure for the surge check. No public manufacturer document names U355A. An open or shorted circuit takes away the main pressure feedback; expect a fuel cell warning and reduced output. Where sensor 2 (U355B) is fitted it can serve as a fallback.

Likely causes

Open, short or corrosion in wiring or connector of sensor 1
Pressure sensor 1 faulty internally
Shared 5 V supply or ground faulty (often with other sensor codes)

Symptoms

  • Fuel cell system warning, MIL on
  • Noticeably reduced power
  • Compressor speed fluctuates or stays high

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

cac outlet pressure sensor 1sensor wiring

Related codes

U355BU355CU3559U355F

References: patents.google.com, patents.google.com.