Network, generic (extended)

U3571 Stack Outlet Coolant Temperature Sensor 1 Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Open, short or corrosion in wiring or connector of outlet sensor 1
Outlet temperature sensor 1 faulty internally or drifting
Connector or wiring near the hot outlet line damaged by heat

Symptoms

  • 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

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–600
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

stack outlet coolant temp sensor 1sensor wiring

Related codes

U3572U3570U3574

References: patents.google.com, patents.google.com, patents.google.com.