What it means
Voltage on the coolant bypass valve A control line is above the expected window. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The engine coolant bypass valve routes coolant around the radiator during warm-up. The control module monitors the valve's control circuit, and this code sets when circuit voltage rises above the expected range, such as when the wire shorts to battery positive or the solenoid circuit opens.
Common causes
Most likely first.
- Control wire shorted to B+
- Open solenoid coil
- Connector pins corroded - high contact resistance
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 see when the high circuit reading occurs.
- With the engine cool, inspect the bypass valve connector and harness for chafing, water entry, corrosion, or damaged insulation.
- Check the control wire for a short to battery positive and inspect connector terminals 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 pass, verify the control module output using the manufacturer's diagnostic procedure.
Common fixes
- Repair a control wire shorted to battery positive.
- Clean or repair corroded bypass-valve connector terminals.
- Replace the bypass valve if its solenoid coil is open.
- Repair a confirmed control module output fault.
Can I keep driving?
You can generally drive if the temperature gauge remains normal, but allow extra warm-up time and stop if the engine overheats. A bypass valve fault can keep the engine from warming efficiently.
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.