What it means
The controller cannot drive the second coolant bypass valve. The associated cooling sub-loop cannot be regulated.
At a glance
- Usually lights the check-engine light
How it works
Coolant bypass valve B controls a second coolant path in the cooling system, and its solenoid receives commands from the control module. This code sets when the module detects an open control circuit and cannot drive the valve B solenoid as intended.
Common causes
Most likely first.
- Open coil in bypass valve solenoid
- Broken control wire
Symptoms
- Check-engine light
- Engine temperature may fluctuate
- Heating or warm-up may be affected
How to diagnose it
- Save freeze-frame data and check scan-tool commands or live data for bypass valve B to confirm when its control fault is detected.
- With the engine cool, inspect valve B's solenoid connector and harness for a loose plug, broken wire, corrosion, or heat damage.
- Check the solenoid coil and control wiring for an open circuit using the wiring information and manufacturer's specification.
- If the coil and wiring are intact, verify the control-side power and command path to valve B under the manufacturer's test procedure.
- Use scan-tool commands, where supported, to see whether valve B responds after an open in its circuit has been ruled out.
Common fixes
- Reconnect a loose bypass valve B solenoid connector.
- Repair a broken or open control wire to valve B.
- Replace corroded or heat-damaged connector terminals.
- Replace the valve B solenoid if its coil is open.
Can I keep driving?
If engine temperature remains normal, drive gently and keep an eye on the temperature gauge, since the valve B cooling sub-loop may not be regulated. Stop if the engine overheats or temperature changes sharply.
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.