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Lights the check engine lamp
U3561: Cathode Bypass Valve Control Circuit
Standardized SAE J2012 code · U35xx codes
What does U3561 mean?
Generic electrical fault on the cathode bypass valve control. Bypass routes air around the stack during startup or low-load operation.
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 U3561 on the same make and model first.
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