What it means
The control module detects that coolant bypass valve C remains open when its commanded position or operating conditions call for it to close. This can alter coolant flow and temperature regulation.
At a glance
- Usually lights the check-engine light
How it works
Coolant bypass valve C directs coolant through a particular path in the engine cooling system. The control module checks whether the valve closes when commanded or when operating conditions require it; this code sets when valve C is detected remaining open, which can keep coolant flowing through the wrong path.
Common causes
Most likely first.
- Valve seized open by sediment
- Broken return spring
Symptoms
- Check-engine light may be on
- Engine takes longer to warm up
- Coolant temperature may fluctuate
How to diagnose it
- Review freeze-frame data and coolant temperature readings to confirm when the valve C stuck-open fault was detected and whether the engine was warming up normally.
- With the engine cool, inspect valve C and its coolant passages for leaks, sediment, or signs that the valve or return spring is damaged.
- Use a scan tool, if supported, to command valve C open and closed and compare its response with the manufacturer's expected operation.
- Check valve C's wiring and connector for damage or poor connections that could prevent it from moving to the commanded position.
- If the electrical checks pass, test the valve's movement and return action using the manufacturer's procedure to distinguish a seized valve from a broken spring.
Common fixes
- Repair a damaged connector or wiring fault preventing valve C from closing.
- Remove sediment from the affected passage and valve if the manufacturer's service procedure permits it.
- Replace valve C if it is seized open.
- Replace the broken return spring or valve assembly as specified for the vehicle.
Can I keep driving?
If the engine is only warming slowly and the temperature remains stable, limit driving and watch the temperature gauge. Stop if it overheats or temperature fluctuates sharply; continued use can worsen temperature regulation and cabin heating.
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.