U3561Cathode Bypass Valve Control Circuit
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U3561 points to a break, a short or an output stage fault in the actuator circuit of the cathode bypass valve. This valve lets part of the compressor delivery skip the stack and flow straight into the exhaust. Nissan gives two reasons: keeping the compressor clear of surge when the stack needs little air, and putting enough air into the exhaust to dilute the hydrogen released when the anode is purged. Because opening the bypass lowers stack pressure, Nissan closes the pressure control valve a little further at the same moment. Toyota uses a three-way valve that can send the entire flow into the bypass when air pressure has to be dumped. No public maker document lists U3561. If the valve cannot be driven, a fuel cell warning is likely, along with limited power and possibly no start. Its mechanical behaviour is judged under U3562.
- What you may notice
- Fuel cell system warning, MIL on
- Reduced power, compressor speed fluctuating at low load
- Fuel cell system does not start
- Likely causes
- LikelyOpen, short or corrosion in wiring or connector of the bypass valve
- PossibleBypass valve motor or actuator faulty
- RareDriver stage of the fuel cell control unit faulty
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €150 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.