What it means
EGR A Control Stuck Open: the control module has detected this fault condition. Without valid EGR feedback the ECU disables exhaust gas recirculation and may set further EGR codes.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The EGR A control system meters exhaust gas back into the intake to reduce combustion temperatures and nitrogen oxide emissions. The control module compares commanded EGR operation with valve feedback or the resulting engine response; P042E sets when EGR A remains more open than commanded, often because carbon or wear prevents the valve from closing.
Common causes
Most likely first.
- Carbon buildup holds valve open
- Carbon or debris buildup preventing free movement
- Component wear with age - mechanical play
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
- Read freeze-frame data and check for related EGR codes, then note idle quality, load, and the EGR command and feedback values.
- Inspect the EGR A valve connector and wiring, and check accessible passages for carbon or debris that could hold the valve open.
- Use a scan tool to compare commanded EGR position with reported position or engine response, especially at idle when the valve should not be stuck open.
- Check whether the valve moves freely and whether the EGR passages or seat are obstructed, following the manufacturer's service information.
- If the valve and passages are clear, test the position feedback circuit and control operation against the manufacturer's specification.
Common fixes
- Clean carbon deposits from the EGR A valve and passages if serviceable.
- Repair a sticking linkage or loose EGR A connector.
- Replace the EGR A valve if it cannot close or its feedback is faulty.
- Repair wiring or control faults confirmed by circuit testing.
Can I keep driving?
Avoid heavy-load driving if the engine pings, hesitates, or loses power, and limit driving if it idles roughly or stalls. Continued operation with EGR A stuck open can worsen drivability and emissions; stop if the engine becomes unsafe to control.
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.