Network
generic or reserved
U3561
Cathode Bypass Valve Control Circuit
Generic electrical fault on the cathode bypass valve control. Bypass routes air around the stack during startup or low-load operation.
SystemNetwork
Typegeneric or reserved
GroupU3
Range / number5 / 61
Possible causes
- Valve actuator failed high
- Gateway module routing CAN messages incorrectly low
- CAN terminating resistor (120 Ω) drifted out of spec low
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
Inspection / repair
- Difficulty: hard
- DIY: shop recommended
- Estimated cost: 300–2500 €
- Estimated time: 1.5–6 h
- Component: cathode bypass valve
- Component: valve wiring
- MIL / check engine light
- drive cycle required
- limp mode possible
Sources
References
sae:J2012