U3573 code meaning
Coolant Mixing Valve Control Circuit
Network system Generic code U35xx codes Check engine light
What U3573 means
U3573 concerns how the coolant mixing valve is powered: its actuator line may be interrupted or shorted, or the output stage may have failed. This three-way valve splits stack coolant between radiator and bypass and so decides how warm it is when it returns to the stack. Designs vary: in a Hyundai application a solenoid pushes a spool and its current sets the split, while Toyota describes a rotary valve turned by a stepper motor through a gear train. In the conventional Hyundai layout the valve takes the stack inlet temperature over CAN from the fuel cell control unit. If the actuator cannot be powered, coolant temperature is no longer regulated. U3573 appears in no public maker document. Likely consequences are a warning and capped output; how the valve itself responds is judged under U3574.
U3573 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U3573
- Fuel cell system warning, MIL on
- Stack temperature too high or too low, reduced power
- Slow warm-up of the fuel cell system
Common causes of U3573
- Most likelyOpen, short or corrosion in wiring or connector of the valve actuator
- PossibleActuator motor or solenoid coil of the mixing valve faulty
- Less likelyDriver stage or CAN link of the controlling unit faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Coolant mixing valveValve wiring
What each part of U3573 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 73 | The exact fault in that area. |
What to do next
- Note U3573 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 U3573
What does U3573 mean?
U3573 means "Coolant Mixing Valve Control Circuit". U3573 concerns how the coolant mixing valve is powered: its actuator line may be interrupted or shorted, or the output stage may have failed. It is a generic code, so it means the same on every make.
Is it safe to drive with U3573?
Drive gently and only to a workshop. With U3573 the car can go into limp mode (reduced power) to protect itself.
Will U3573 fail an emissions test?
U3573 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 U3573 to fix?
Difficulty: hard. A typical repair takes 1 to 3 hours of work. This is a job for a workshop.
Will U3573 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.