What it means
The controller cannot drive the engine coolant bypass valve A. The valve usually routes coolant around the radiator during warm-up; without it warm-up takes longer and emissions during the warm-up phase rise.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The engine coolant bypass valve routes coolant around the radiator during warm-up so the engine can reach operating temperature efficiently. This code sets when the control module detects an open in the valve control circuit and cannot operate the valve as expected.
Common causes
Most likely first.
- Open coil in bypass valve solenoid
- Broken control wire
Symptoms
- Check-engine light
- Longer engine warm-up
- Temperature gauge may take longer to rise
How to diagnose it
- Record freeze-frame data and check coolant temperature and bypass-valve command data to confirm the fault occurs during warm-up.
- With the engine cool, inspect the bypass valve connector and wiring for a disconnected plug, broken wire, corrosion, or heat damage.
- Check the circuit fuse and verify supply and control wiring continuity using the manufacturer's wiring information.
- Test the bypass valve solenoid coil for an open circuit and compare the result with the manufacturer's specification.
- If the valve and wiring are intact, check the control module output using the manufacturer's diagnostic procedure.
Common fixes
- Reconnect the bypass valve plug if it is loose or disconnected.
- Repair a broken control wire or corroded connector terminal.
- Replace the bypass valve if its solenoid coil is open.
- Repair the control module output circuit if testing confirms it is faulty.
Can I keep driving?
You can generally drive if the temperature gauge remains normal, but allow extra warm-up time and avoid driving if the engine overheats. Extended cold running can increase fuel use and warm-up emissions.
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.