P042E
EGR A Control Stuck Open
EGR (emissions)
Generic OBD-II
Medium
What it means
P042E means the engine computer has detected that the 'A' exhaust gas recirculation (EGR) valve is stuck open. With the valve stuck open, too much exhaust gas enters the intake at idle and light load, which dilutes the mixture and causes a rough idle, hesitation, and sometimes stalling. Carbon buildup is the most common cause.
Medium
Can I keep driving? Drivable but often rough — a stuck-open EGR valve floods the intake with exhaust at idle, causing a rough idle, hesitation, and sometimes stalling until repaired.
Common symptoms
What you'll notice
- Check-engine light on
- Rough, unstable idle
- Hesitation or stumble on light acceleration
- Stalling at idle or when coming to a stop
Common causes
Most likely first
- Carbon buildup in the EGR valve or passages holding the valve openLikely
- Faulty or sticking EGR valveCommon
- Stuck EGR vacuum/control solenoid or a leaking vacuum lineCommon
- Wiring or feedback-signal fault preventing the ECM from closing the valveLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data, then remove and clean the EGR valve, tube, and passages of carbon before replacing parts.
- Inspect the valve for a torn diaphragm or a stuck pintle and confirm it seats fully closed.
- Check the EGR control solenoid and its vacuum/electrical signal.
- Verify the position-feedback circuit, then replace the EGR valve if it won't seal. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P042E?+
Short-term yes, but the rough idle and possible stalling make it unpleasant and it will fail emissions. Clean or repair the EGR valve soon.
Can I just clear P042E?+
You can, but if the valve is stuck open the code returns and the rough idle continues until it's cleaned or replaced.
Related codes
Often seen with P042E
Read & clear P042E yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX