What it means
Generic fault on the coolant mixing valve — combines circuit and mechanical issues. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.
At a glance
- Usually lights the warning light of the system that lost communication
How it works
The coolant mixing valve blends hot and cold coolant streams to help maintain fuel cell stack temperature. This code indicates a fault associated with the valve as a whole, which can involve its electrical control, mechanical movement, or communication with other modules.
Common causes
Most likely first.
- Valve electrical or mechanical failure
- 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 valve, temperature-control, and CAN communication faults.
- Review commanded valve position and available coolant temperature data to see whether the valve appears to respond as requested.
- Inspect the valve body, connectors, and harness for damage, leakage, loose connections, or signs that the valve is obstructed.
- Check valve electrical operation and mechanical movement using the manufacturer's service information and specification.
- If several modules report communication faults or no response, check gateway routing and CAN wiring and termination to the manufacturer's specification.
Common fixes
- Reconnect or repair damaged valve wiring or connectors.
- Clear an obstruction or repair a mechanical fault in the mixing valve, where serviceable.
- Replace a failed coolant mixing valve or actuator assembly.
- Correct gateway routing or repair faulty CAN wiring or termination.
Can I keep driving?
Do not continue driving through stack temperature warnings, reduced power, or a fuel cell shutdown; improper coolant mixing can compromise stack temperature control. Stop when the vehicle issues a stop 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.