Network, generic (extended)

U3570 Stack Inlet Coolant Temperature Sensor Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3570 signals that the sensor for coolant entering the stack sends a broken, shorted or out-of-range reading. Thermal control is steered by this value: Hyundai describes a three-port valve which gets the stack inlet temperature from the fuel cell control unit over CAN and sets its opening from it, and in a Nissan patent the current drawn from the stack is capped once inlet coolant passes a set point, so that the outlet cannot overheat. GM shows that the inlet figure can also be estimated from pump inlet temperature, flow rate and a heat exchanger model. No maker documents U3570 publicly. Without a valid reading the system has to run on a substitute; a warning lamp and held-back power are to be expected. Outlet sensors report as U3571 and U3572.

Likely causes

Open, short or corrosion in wiring or connector of the inlet sensor
Inlet coolant temperature sensor faulty internally (drift, internal open)
Coolant seeping past the sensor seal into the connector
Input stage of the fuel cell control unit faulty

Symptoms

  • Fuel cell system warning, MIL on
  • Reduced power, especially under high load
  • Implausible stack inlet temperature 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 inlet coolant temp sensorsensor wiring

Related codes

U3571U3572U3573U3574

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