What it means
The turbocharger or supercharger boost control B circuit is intermittent or erratic.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Boost control B is the electrical circuit and actuator mechanism used to regulate turbocharger or supercharger boost. This code means the computer sees the control B signal or operation vary unpredictably, often because vibration interrupts a connector or harness connection.
Common causes
Most likely first.
- Connector loose or corroded
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine light on
- Reduced engine performance
How to diagnose it
- Save freeze-frame data and examine control B feedback alongside commanded and actual boost for dropouts.
- Inspect the control B connector for looseness, corrosion, or pins that may lose contact when shaken.
- Trace the control B harness and check for chafing or contact with a vibrating engine component.
- Monitor control B feedback while gently moving the harness and connector to reproduce an intermittent fault.
- Check the circuit and actuator for intermittent opens or shorts using the manufacturer's test procedure.
Common fixes
- Reseat and secure the control B connector.
- Clean or repair corroded or loose connector terminals.
- Repair chafed wiring and secure the harness away from vibrating parts.
- Replace a boost control B actuator only if it fails testing with a sound circuit.
Can I keep driving?
Drive gently and avoid hard acceleration or heavy loads because boost may drop unexpectedly and performance can be reduced. If the engine enters limp mode or power loss makes traffic unsafe, pull over safely.
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.