What it means
EGR sensor B signal jumps or drops out intermittently. EGR mixes inert exhaust into intake to lower combustion peak temperature — too little raises NOx, too much causes misfires and rough running.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
EGR sensor B sends a signal that the control module uses to monitor EGR operation. This code sets when that signal jumps, drops out, or changes erratically instead of remaining stable as EGR operation changes.
Common causes
Most likely first.
- Intermittent connector
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
How to diagnose it
- Check freeze-frame data and graph EGR sensor B live data to identify whether the dropout occurred at a particular load, temperature, or engine speed.
- Inspect sensor B's connector for loose locking, corrosion, moisture, or terminals that may lose contact under vibration.
- Trace the sensor B harness and look for chafing or contact with a vibrating or hot component.
- With the engine running and live data displayed, gently move the accessible harness and connector to see whether sensor B's signal cuts out.
- Test sensor B's supply, ground, and signal wiring for intermittent opens or shorts using the vehicle wiring diagram and manufacturer's specification.
- If the connector and harness remain stable during testing, check sensor B for an internal intermittent fault and replace it if confirmed.
Common fixes
- Reseat and secure the EGR sensor B connector.
- Clean corroded terminals or repair terminals that do not grip securely.
- Reroute and secure the harness away from vibration, heat, or rubbing points.
- Repair an intermittent open or short in the sensor B wiring.
- Replace EGR sensor B if its signal still drops out with a sound connector and harness.
Can I keep driving?
A short, gentle drive may be possible if the engine remains smooth, but avoid heavy loads because an erratic EGR signal can cause hesitation or knocking and may increase emissions. Stop driving if the engine begins misfiring or loses substantial power.
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.