P0403: EGR A Control Circuit/Open

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. P0403 concerns the electrical drive of the EGR valve – solenoid, stepper motor, DC motor or vacuum regulator. The module checks the output and sets the code for an open circuit (GM: above 200 kΩ, MIL after two trips; Ford after 4 s, MIL after two trips). Newer systems report shorts separately as P0489 (low) and P0490 (high); Ford and older GM systems include them in P0403. EGR is then switched off for the rest of the trip.

Medium severity. Can I keep driving?Normally yes, without pushing the engine, as far as a repair shop. Many cars disable the EGR or reduce power, and if the valve stays open the idle may become unstable.

Symptoms

Check engine light on
EGR switched off: pinging (petrol) or higher NOx
Usually no loss of power

Most likely causes

Connector at the EGR valve corroded or loose
Broken control or supply wire
Coil or motor in the EGR valve burnt out
Driver in the engine module

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and any vacuum hoses
Check the continuity of the wire between the component and the control module.
Use live data to compare the commanded opening with the actual opening
Clean the valve and passages if they are clogged with carbon
Test the actuator with the scanner
Replace the valve if it still does not follow the command after cleaning

Good to know

Repair difficulty: easy
It affects emissions.

What each character of P0403 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
4: Emissions
03: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0403?

Normally yes, without pushing the engine, as far as a repair shop. Many cars disable the EGR or reduce power, and if the valve stays open the idle may become unstable.

What causes code P0403?

The most common causes are: connector at the EGR valve corroded or loose; broken control or supply wire; coil or motor in the EGR valve burnt out.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.