U3562Cathode Bypass Valve
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- Unlike U3561, this code concerns how the cathode bypass valve itself behaves: it does not reach or hold the opening the controller asks for, for instance because it sticks. A Toyota patent shows why a valve stuck shut is serious. While a cold stack is warmed by deliberately inefficient generation, bypass air is supposed to thin out hydrogen in the exhaust; if ice holds the valve closed, all of that air enters the stack, which then produces more power than intended. Toyota spots this from compressor outlet pressure above a limit or from stack current straying from its command, then opens the backpressure valve and slows the compressor. A valve stuck open costs stack pressure instead, as Nissan notes. No maker publishes U3562; that stuck air valves switch on the MIL is documented by Toyota for the Mirai (T-SB-0043-23).
- What you may notice
- Fuel cell system warning, MIL on
- Reduced power or failed start in frost
- Unusual compressor or air noise
- Likely causes
- PossibleValve frozen in place after a cold soak
- PossibleValve sticking from deposits or wear
- PossibleActuator too weak or gear damaged
- RarePosition feedback reading wrong, valve itself fine
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €300 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.