OBD-II code · Network (extended)
U355F Cathode Backpressure Valve Control Circuit
Generic electrical fault on the cathode back-pressure valve control. The valve regulates pressure on the cathode (air) side of the fuel cell stack.
Is it safe to drive with U355F?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyValve actuator failed
- Less likelyGateway module routing CAN messages incorrectly
- Less likelyCAN terminating resistor (120 Ω) drifted out of spec
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
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1.5–6 h
- Emissions test
- Usually unaffected
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Cathode Backpressure Valve, Valve Wiring
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.