P0403

EGR A Control Circuit/Open

EGR / emissions Generic OBD-II Medium

What it means

P0403 means the ECM has detected an open or fault in the electrical circuit that controls the exhaust gas recirculation (EGR) valve. The EGR system routes a little exhaust back into the intake to lower combustion temperatures and emissions. When the control circuit is open, EGR may not operate, which can cause rough idle, mild knock, and an emissions failure.

Medium

Can I keep driving? Usually drivable — you may notice rough idle, light knock, or hesitation, but it's mainly an emissions fault.

Real-world scan data

Seen in

4,018

scans in the past year

Found in

0.6%

of scans

1.1%

of scans that found faults

Appears alongside · share of P0403 scans

P0683in 22.4% of scans

P0110in 19.7% of scans

P0100in 15.1% 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 idle or mild hesitation
Light engine knock or pinging under load
Failed emissions test

Common causes

Most likely first

Open or damaged wiring in the EGR control circuit (most common)Likely
Faulty EGR valve or control solenoidCommon
Corroded or loose connector at the EGR valveCommon
Faulty ECM or EGR driver (rare)Less often

How to diagnose & fix

Work through it in order

Inspect the EGR valve/solenoid connector and wiring for an open circuit or corrosion.
Measure the solenoid's coil resistance and compare it to spec.
Verify the ECM is sending the control signal to the valve.
Replace the EGR valve or solenoid if it's failed.
Only consider the ECM after wiring and the valve test good. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0403?+

Usually yes for short-term driving, but incorrect EGR operation can cause knock and raise emissions, so don't leave it unrepaired.

Can I just clear P0403?+

It returns once the ECM detects the open control circuit again, so the wiring or EGR valve fault must be fixed first.

Read & clear P0403 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