What it means
Generic electrical fault on the coolant mixing valve control. The valve blends hot and cold coolant streams to maintain stack temperature.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
The coolant mixing valve actuator controls how hot and cold coolant streams blend to regulate fuel cell stack temperature. This code indicates an electrical or control fault associated with the valve circuit, and a gateway or CAN termination problem may also interrupt its commands or status.
Common causes
Most likely first.
- Valve actuator failed
- Gateway module routing CAN messages incorrectly
- CAN terminating resistor (120 Ω) drifted out of spec
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Record freeze-frame data and scan all modules for communication codes and valve-related faults before clearing anything.
- Check live data for the commanded mixing-valve position and any available status or temperature changes that indicate whether the command is being received.
- Inspect the valve actuator connector and harness for looseness, corrosion, chafing, or damage.
- Check actuator power, ground, control wiring, and operation using the vehicle's service information and the manufacturer's specification.
- If communication faults span multiple modules, check gateway routing and CAN wiring and termination against the manufacturer's specification.
Common fixes
- Reconnect or repair a damaged actuator connector or harness.
- Repair a faulty actuator power, ground, or control circuit.
- Replace a failed coolant mixing valve actuator.
- Correct gateway routing or repair CAN wiring and termination if network checks identify a fault.
Can I keep driving?
Avoid continued use if the vehicle reports stack temperature warnings, reduced power, or a fuel cell system shutdown, since the valve may not regulate coolant mixing correctly. Follow any stop or shutdown warning.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.