What it means
The control module detects that coolant bypass valve D 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 D directs coolant through a particular path in the engine cooling system. The control module checks whether valve D closes when commanded or when operating conditions require it; this code sets when valve D is detected remaining open, which can disrupt coolant flow and temperature regulation.
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 D stuck-open fault occurred and whether the engine was warming normally.
- With the engine cool, inspect valve D and its coolant passages for leaks, sediment, or signs of a damaged valve or return spring.
- Use a scan tool, if supported, to command valve D open and closed and compare its response with the manufacturer's expected operation.
- Check valve D's wiring and connector for damage or poor connections that could prevent it from moving to the commanded position.
- If electrical checks pass, test valve D'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 D from closing.
- Remove sediment from the affected passage and valve if the manufacturer's service procedure permits it.
- Replace valve D 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 warming slowly but its temperature stays stable, limit driving and watch the gauge. Stop if it overheats or temperature fluctuates sharply, as continued use can worsen temperature control 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.