Network, generic (extended)

U3575 Coolant Mixing Valve Position Sensor Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3575 deals with wiring and signal of the sensor reporting how far the coolant mixing valve is open. GM lists feedback of the valve position, next to two temperature sensors, among the parts its stack outlet temperature control relies on. In Toyota's design the sensor is built into the valve and returns the angle of the valving element; since it can drift, the controller re-zeroes it against an end position before the coolant pump starts. If the signal is missing or shorted, the controller no longer knows where the valve stands and may regulate from temperatures alone or move the valve to a safe setting. No maker documents U3575 publicly. Probable results: a warning lamp and capped output. Faults in driving this valve fall under U3573.

Likely causes

Open, short or moisture in the position sensor wiring or connector
Position sensor faulty (usually replaced together with the valve)
Sensor supply or ground missing

Symptoms

  • Fuel cell system warning, MIL on
  • Stack temperature regulated less precisely, reduced power
  • Valve opening shown as invalid in live data

Repair estimate

DifficultyHardWorkshop job
Parts and labour€200–1,200
Time1–3 h

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

Parts involved

coolant mixing valve position sensorsensor wiring

Related codes

U3573U3574U3570

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