What it means
EGR throttle B drive line stuck high — short to B+. 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
The EGR throttle regulates intake airflow used to meter exhaust gas recirculation. The control module monitors drive circuit B for an abnormally high electrical level; a short to battery voltage can stop the actuator responding correctly and disrupt EGR flow.
Common causes
Most likely first.
- Signal or control wire shorted to power
- Chafed wiring contacting a power source
- Corroded or bridged connector pins
- Faulty EGR throttle actuator or driver
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
- Record freeze-frame data and compare commanded EGR throttle position with available position and EGR data to identify when circuit B went high.
- Inspect the EGR throttle B connector and harness for insulation damage, corrosion, bridged pins, or contact with a powered wire.
- With the circuit isolated as directed by the manufacturer, check whether circuit B is unintentionally connected to battery voltage.
- Test the actuator and driver circuit using the manufacturer's procedure to separate a harness short from an internal actuator or driver fault.
- After repair, clear the code and confirm circuit B and EGR operation during a suitable drive cycle.
Common fixes
- Repair wiring where EGR throttle circuit B contacts a power source.
- Clean or repair corroded, damaged, or bridged connector pins.
- Replace a failed EGR throttle actuator if its circuit tests identify an internal fault.
- Repair the control module driver only after wiring and actuator checks confirm the driver has failed.
Can I keep driving?
If the engine runs smoothly, a short gentle trip may be possible, but avoid heavy loads if it pings, hesitates, or loses power. Incorrect EGR flow can increase NOx emissions and worsen drivability.
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.