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.

Real-world scan data

Seen in

824

scans in the past year

Found in

0.1%

of scans

0.2%

of scans that found faults

Appears alongside · share of P042E scans

P042Fin 41.9% of scans

P0406in 22.1% of scans

P0487in 22.0% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear P042E yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX