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U3576 Stack Differential Pressure Sensor Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3576 is set when the stack differential pressure sensor delivers no signal, a shorted one or one outside its valid range. The title leaves open which two pressures it compares. In a GM patent such a sensor is plumbed between anode and cathode side, as the anode is normally kept slightly above the cathode. GM also uses it ahead of start-up, with the cathode still at ambient pressure, to verify the anode pressure sensor: ambient plus differential reading should match the anode value. Ford keeps the difference across the membrane within a tolerance of around 600 mbar, may shut the system down when it is breached and heats such sensors so that ice cannot blind them. No maker documents U3576 publicly. Expect a warning, reduced power or no start; anode inlet pressure is U3566/U3567.

Likely causes

Open, short or corrosion in wiring or connector of the differential pressure sensor
Water or ice in the sensor ports or a failed sensor heater
Differential pressure sensor faulty internally

Symptoms

  • Fuel cell system warning, MIL on
  • Reduced power or fuel cell system shuts down
  • No start, especially after a cold night

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–900
Time0.5–3 h

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

Parts involved

stack differential pressure sensorsensor wiring

Related codes

U3566U3567U356D

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