What it means
The control module detects that coolant bypass valve D remains closed when it is commanded to open. This can restrict coolant flow through the affected part of the cooling system.
At a glance
- Usually lights the check-engine light
How it works
Coolant bypass valve D controls flow through one path in the engine cooling system. The control module checks whether valve D opens when commanded; this code sets when it detects the valve remaining closed, which can restrict flow through the affected part of the system.
Common causes
Most likely first.
- Valve seized closed by debris
- Actuator linkage jammed in closed position
- Carbon or debris buildup preventing free movement
Symptoms
- Check-engine light may be on
- Engine may overheat
- Cabin heat may be reduced
How to diagnose it
- Check freeze-frame data and live coolant temperature for signs of rising temperature or overheating when valve D was expected to open.
- With the engine cool, inspect valve D and the affected coolant passage for debris, sediment, or damage that could block flow.
- Use a scan tool, if supported, to command valve D open and check whether its feedback or observed response changes as expected.
- Inspect valve D's actuator linkage and wiring for a jam, damage, or connection fault that could hold the valve closed.
- If the electrical supply and linkage are sound, test the valve for restricted movement using the manufacturer's procedure.
Common fixes
- Clear debris from the valve D passage if the manufacturer's service procedure allows it.
- Free or repair a jammed valve D actuator linkage.
- Replace valve D if it is seized closed or cannot move freely.
- Repair damaged wiring or connector faults that prevent valve D from opening.
Can I keep driving?
Do not continue driving if the temperature gauge rises above normal, an overheating warning appears, or coolant is being lost; stop safely and let the engine cool. A closed valve D can restrict coolant flow and cause serious engine damage, and cabin heat may also be reduced.
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.