U3563 code meaning
Cathode Bypass Valve Position Sensor Circuit
Network system Generic code U35xx codes Check engine light
What U3563 means
U3563 means the position sensor on the cathode bypass valve delivers no usable signal because of a broken wire, a short or a voltage outside its window. Toyota's patent mounts such a valve body position sensor right at the bypass valve, with pressure sensors before and after it; the angle tells the controller how the compressor air is really being split between stack and bypass. A Hydrogenics patent likewise fits angle sensors to the throttle-type valves of its stack. No public manufacturer source names U3563. Without the feedback, the controller has to infer the valve state indirectly, for example from compressor outlet pressure or stack current as Toyota describes, and will usually restrict operation. Drive faults of the valve are U3561, a mechanically misbehaving valve U3562.
U3563 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U3563
- Fuel cell system warning, MIL on
- Reduced power, especially at low load
Common causes of U3563
- Most likelyOpen, short or moisture in the position sensor wiring or connector
- PossiblePosition sensor in the valve unit faulty
- Less likelyShared 5 V supply or ground faulty (often with other sensor codes)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cathode bypass valve position sensorSensor wiring
What each part of U3563 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 63 | The exact fault in that area. |
What to do next
- Note U3563 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U3563
What does U3563 mean?
U3563 means "Cathode Bypass Valve Position Sensor Circuit". U3563 means the position sensor on the cathode bypass valve delivers no usable signal because of a broken wire, a short or a voltage outside its window. It is a generic code, so it means the same on every make.
Is it safe to drive with U3563?
Drive gently and only to a workshop. With U3563 the car can go into limp mode (reduced power) to protect itself.
Will U3563 fail an emissions test?
U3563 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U3563 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U3563 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.