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Lights the check engine lamp
U355F: Cathode Backpressure Valve Control Circuit
Standardized SAE J2012 code · U35xx codes
What does U355F mean?
Generic electrical fault on the cathode back-pressure valve control. The valve regulates pressure on the cathode (air) side of the fuel cell stack.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
- High Valve actuator failed
- Low Gateway module routing CAN messages incorrectly
- Low CAN terminating resistor (120 Ω) drifted out of spec
Likelihood is a general estimate across vehicles; your make and model may differ.
Add your car to see reports of U355F on the same make and model first.
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