What it means
Voltage on the second coolant bypass valve 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 control module drives the solenoid for coolant bypass valve B to regulate a second coolant path. This code sets when voltage on valve B's control circuit falls below the expected range, which can point to a short to ground or a fault in the solenoid or connector.
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
- Engine temperature may fluctuate
- Heating or warm-up may be affected
How to diagnose it
- Record freeze-frame data and check valve B command and circuit data with a scan tool to establish when the low reading occurs.
- Inspect bypass valve B's connector and control harness for chafing, moisture, corrosion, backed-out pins, or a wire touching ground.
- With the fault active, gently move the harness near valve B while watching circuit data or the code status for a change.
- Check the control wire for a short to ground and inspect the solenoid coil and connector contact, following the wiring information and manufacturer's specification.
- If the harness is sound, test valve B's solenoid for an internal short and verify the control output.
Common fixes
- Clean and secure valve B's connector, replacing damaged or corroded terminals.
- Repair the control wire where it is shorted to ground or chafed.
- Repair a poor connector contact or damaged circuit connection.
- Replace the bypass valve B solenoid if its coil is internally shorted.
Can I keep driving?
If engine temperature stays normal, drive gently and monitor it because bypass valve B may not regulate its cooling path correctly. Stop if the temperature rises above normal or the engine overheats.
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.