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.
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.
Related codes
Often seen with P0403
Read & clear P0403 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