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U355B Charge Air Cooler Outlet Pressure Sensor 2 Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U355B points to a circuit problem with pressure sensor 2 at the charge air cooler outlet. J2012 lists two at this spot, which points to a pair used for cross-checking; how a maker splits the roles is unpublished, and no public document uses U355B. A GM patent shows the principle: before start-up, while the compressor stands still and the cathode holds only atmospheric pressure, readings are compared, and a doubtful sensor is replaced by a value calculated from the remaining ones. Ford names a winter risk on the wet air side: water on a sensor diaphragm can freeze and give no or false output at a cold start, which may lead to a shutdown. Sensor 1 at the same spot is U355A. With only one valid sensor left, output may be limited.

Likely causes

Open, short or corrosion in wiring or connector of sensor 2
Condensed water frozen on the sensor (occurs at cold start, may clear when warm)
Pressure sensor 2 faulty internally

Symptoms

  • Fuel cell system warning, MIL on
  • Start refused or system shuts down shortly after a cold start
  • Reduced power while only one pressure sensor is valid

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 2sensor wiring

Related codes

U355AU355CU3559

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