Network, generic (extended)

U3572 Stack Outlet Coolant Temperature Sensor 2 Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3572 is logged when the second coolant temperature sensor at the stack outlet has a wiring or signal problem. No maker explains in public why two sensors share this spot; mutual checking is the obvious reason. A Toyota patent for systems with several stacks shows one way: outlet temperature is estimated from inlet temperature and stack output, and an outlet sensor whose reading departs from that estimate is reported as faulty. GM compares the outlet value with an expected figure to spot a failed coolant pump and may then lower stack output. Hyundai campaign 21-01-045H-1 for the Nexo shows that a stack coolant fault (pump code P1D3D94) lights the check engine lamp. No maker documents U3572 publicly. With sensor 1 still valid a warning may be all; with both lost, power will be cut. Sensor 1 is U3571.

Likely causes

Open, short or corrosion in wiring or connector of outlet sensor 2
Outlet temperature sensor 2 faulty internally
Shared sensor ground faulty (often with U3571 at the same time)

Symptoms

  • Fuel cell system warning, MIL on
  • Little or no change in driving as long as sensor 1 is valid
  • Reduced power if both outlet sensors are affected

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 2sensor wiring

Related codes

U3571U3570U3574

References: patents.google.com, patents.google.com, static.nhtsa.gov.