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U3560 Cathode Backpressure Valve Position Sensor Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3560 is set when the signal of the position sensor on the cathode backpressure valve is missing, shorted or outside its electrical range. Outlet valves of this kind are often throttle flaps whose angle is reported back, as a Hydrogenics patent shows for the cathode and purge valves of a stack. The reading matters beyond the valve: in a GM patent the controller turns the valve position into an expected air-side pressure and compares it with the measured one to reveal leaks or blockages in the air path, so without a believable angle that check loses its footing. No manufacturer publishes U3560. The controller may carry on regulating from pressure alone or park the flap in a safe position; a warning and limited output are likely. Faults in powering the same valve are logged as U355F.

Likely causes

Open, short or moisture in the position sensor wiring or connector
Position sensor faulty (often only available with the valve unit)
Sensor 5 V supply or ground missing

Symptoms

  • Fuel cell system warning, MIL on
  • Reduced power
  • Further air path codes stored at the same time

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–1,200
Time0.5–3 h

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

Parts involved

cathode backpressure valve position sensorsensor wiring

Related codes

U355FU3563U3561U355D

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