What it means
Voltage on the coolant bypass valve A control line is below 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 falls below the expected range, often because of a short to ground or a shorted solenoid.
Common causes
Most likely first.
- Control wire shorted to ground
- Internal short in 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 identify when the low circuit reading occurs.
- With the engine cool, inspect the bypass valve connector and harness for chafing, water entry, corrosion, or damaged insulation.
- Check whether the control wire is shorted to ground and inspect connector terminal contact using the manufacturer's wiring information.
- Test the bypass valve solenoid for an internal short and compare the result with the manufacturer's specification.
- If the valve and wiring pass, verify the control module circuit output using the manufacturer's diagnostic procedure.
Common fixes
- Repair a control wire shorted to ground.
- Clean or repair corroded bypass-valve connector terminals.
- Replace the bypass valve if its solenoid is internally shorted.
- Repair a confirmed fault in the control module output circuit.
Can I keep driving?
You can generally drive if the temperature gauge stays normal, but allow extra warm-up time and avoid driving if the engine overheats. Prolonged cold operation 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.