U356A code meaning
Anode Drain Valve Control Circuit
Network system Generic code U35xx codes Check engine light
What U356A means
U356A concerns the electrical drive of the solenoid sitting under the anode water trap, which lets condensate leave the hydrogen loop. Hyundai opens it when a level sensor reports a full trap and closes it at a low mark so no hydrogen follows; if that sensor fails, the valve is closed as soon as anode pressure falls faster than a set rate. GM also gives the drain valve an emergency role: after an injector sticks open, hydrogen may be let out through it until the concentration in the exhaust reaches a limit. A broken or shorted drive circuit takes away both jobs. No maker documents U356A publicly. Since water keeps collecting in the anode, a warning and reduced or interrupted operation are plausible. The valve's mechanical state is U356B, the header drain circuit U356C.
U356A 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 U356A
- Fuel cell system warning, MIL on
- Reduced power after some driving time
- Fuel cell system shuts down
Common causes of U356A
- Most likelyOpen, short or corrosion in wiring or connector of the drain valve
- PossibleDrain valve solenoid coil open or shorted
- Less likelyDriver stage of the fuel cell control unit faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Anode drain valveValve wiring
What each part of U356A means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 6A | The exact fault in that area. |
What to do next
- Note U356A 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 U356A
What does U356A mean?
U356A means "Anode Drain Valve Control Circuit". U356A concerns the electrical drive of the solenoid sitting under the anode water trap, which lets condensate leave the hydrogen loop. It is a generic code, so it means the same on every make.
Is it safe to drive with U356A?
Drive gently and only to a workshop. With U356A the car can go into limp mode (reduced power) to protect itself.
Will U356A fail an emissions test?
U356A 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 U356A to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U356A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.