U3572
Stack Outlet Coolant Temperature Sensor 2 Circuit.
- Generic
- Network
- Generic code
- Medium severity
How this code is built
- U
- SystemNetwork
- 3
- Defined bySAE, the same on every car
- 5
- AreaNetwork area 5
- 72
- FaultThe specific fault in that area
What it means
U3572 is defined as a Stack Outlet Coolant Temperature Sensor 2 circuit fault. It applies to vehicles with a fuel cell stack, where the coolant temperature at the stack outlet is monitored. The controlling module has seen a signal from this sensor, or a message carrying its value, that is missing, out of range or implausible. The U prefix suggests the fault may involve communication or data between modules, so the exact detection method depends on the vehicle.
Symptoms
- Warning light or fuel cell system fault message on the dashboard
- Reduced power or the vehicle going into a limited performance mode
- Cooling fan or coolant pump running harder than normal
- Fuel cell system shutting down, or refusing to start or ready up
- Other fuel cell or communication fault codes stored alongside it
Possible causes
- Faulty stack outlet coolant temperature sensor 2likely
- Damaged, chafed or corroded wiring to the sensor, including open circuit, short to ground or short to supplylikely
- Poor connection at the sensor or control module connector, such as water ingress, corrosion or loose pinslikely
- Loss of or corrupted data between the module that reads the sensor and the module that reports the faultpossible
- Coolant level, air in the system or flow problem causing implausible readings compared with the other stack temperature sensorspossible
- Fault inside the fuel cell control module, or an outdated calibration where the manufacturer has issued an update for this faultrare
How to diagnose
- Read all stored and pending codes and freeze frame data, and note whether network or communication codes are also present.
- Check for manufacturer service bulletins and software updates relevant to the model and fuel cell system.
- Check the coolant level and condition, and look for leaks, as the correct coolant type and bleed procedure are model specific.
- Inspect the sensor, its wiring and connectors for damage, corrosion, moisture and pin fit.
- Compare live data from sensor 2 with the other stack coolant temperature sensors on a cold system. Readings should be close to each other and to ambient temperature.
- Follow the manufacturer's procedure to measure sensor resistance and check supply, signal and ground wiring for continuity and shorts. Use only trained personnel and the correct isolation steps near high-voltage components.
- Check the module network for communication faults and the health of the relevant control modules' power and earth supplies.
- After repair, clear the codes and road test, then confirm the code does not return and the readings are plausible.
How to fix
- Replace the stack outlet coolant temperature sensor 2 if it is out of specification or its readings are implausible.
- Repair or replace damaged wiring and clean or renew corroded or loose connectors.
- Correct the coolant level and bleed air from the cooling system using the manufacturer's procedure.
- Repair any network or module power and earth supply fault found.
- Apply a manufacturer-issued software update if the fault is a known calibration issue, or replace the control module if it is confirmed faulty.
Can I keep driving?
The vehicle may be driven carefully for a short time if it runs normally, but get it checked soon. Without a reliable stack temperature reading, the system may limit power or shut down to protect the stack, so stop if warnings escalate or the temperature rises.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.