U3571 code meaning
Stack Outlet Coolant Temperature Sensor 1 Circuit
Network system Generic code U35xx codes Check engine light
What U3571 means
U3571 concerns the wiring and signal of sensor 1 in the coolant stream leaving the stack. Coolant is hottest here, so the reading serves as the main overheat guard: GM holds stack outlet temperature mainly with a three-port valve sending coolant past or through the radiator and shuts the stack off when coolant at this point gets too hot. A wrong outlet value can therefore force a needless shutdown or hide genuine overheating. GM cross-checks the sensor against end cell temperatures and treats it as suspect when it reads more than 3 °C above their average. Hyundai can fall back on the exhaust temperature of the air side as a stand-in. No public maker document names U3571. Warning and lower output follow; U3572 covers sensor 2 at this location, U3570 the inlet.
U3571 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U3571
- Fuel cell system warning, MIL on
- Power reduced or fuel cell system switched off as a precaution
- Outlet temperatures of sensor 1 and sensor 2 disagree in live data
Common causes of U3571
- Most likelyOpen, short or corrosion in wiring or connector of outlet sensor 1
- PossibleOutlet temperature sensor 1 faulty internally or drifting
- Less likelyConnector or wiring near the hot outlet line damaged by heat
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Stack outlet coolant temp sensor 1Sensor wiring
What each part of U3571 means
| U | Network system: communication between the control modules (CAN bus). |
| 3 | Reserved range, usually generic. |
| 71 | The exact fault in that area. |
What to do next
- Note U3571 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 U3571
What does U3571 mean?
U3571 means "Stack Outlet Coolant Temperature Sensor 1 Circuit". U3571 concerns the wiring and signal of sensor 1 in the coolant stream leaving the stack. It is a generic code, so it means the same on every make.
Is it safe to drive with U3571?
Drive gently and only to a workshop. With U3571 the car can go into limp mode (reduced power) to protect itself.
Will U3571 fail an emissions test?
U3571 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 U3571 to fix?
Difficulty: hard. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will U3571 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.