Code P0403: Exhaust Gas Recirculation Circuit Malfunction

What Is an Exhaust Gas Recirculation Circuit?

In order to reduce emissions and improve fuel economy, your vehicle has an exhaust gas recirculation, or EGR, system. Your EGR system uses a series of hoses and a charcoal filter canister to store fuel vapors until your engine turns on. Once the ignition is activated, your powertrain control module activates a vacuum solenoid to draw fuel vapors into your engine.

This complex system also has a control circuit, or driver, to prevent any risk caused by a circuit malfunction. Your powertrain control module uses this fault circuit to monitor the normal operation of electricity. When the vacuum solenoid is off, the control circuit should be near the same voltage as your battery. When the solenoid is activated, the relevant control circuit should have little or no voltage. Any issue with this circuit triggers trouble code P0403.

So, what does the code P0403 mean? It’s most likely an electrical issue, but it could be a sign that your EGR system isn’t working properly. Look for common symptoms and causes to determine the correct solution.

Common Symptoms

If the issue is only with the control circuit, you won’t experience any performance issues. Your malfunction indicator lamp will light up, but otherwise your vehicle will be unaffected.

However, this trouble code could also be a sign of a faulty or stuck vacuum solenoid. In that case, your EGR system isn’t sealed and fuel vapors may be escaping. Look for a rough idle, sudden engine dying, under acceleration or occasional misfiring for signs that your EGR vacuum solenoid may be damaged.

Potential Causes

For many trouble code P0403 instances, there’s a short in the fault circuit. You may need to repair the control circuit to remove this error code. However, there are a range of series, if rare, issues that could also alert this trouble code. It’s important to inspect your vehicle carefully for any of these potential causes:

• Stuck EGR solenoid
• Damaged EGR solenoid
• Frayed, loose or wet wiring harness at the EGR solenoid
• Damaged powertrain control module

After inspecting the fault circuit, check each of these components for any signs of visible damage, any loss of voltage or excessive resistance. Each of these could also cause trouble code P0403 or related trouble codes in the P0400 range, such as P0401, P0402, etc.

Repairs and Other Solutions

First, check turn off your engine while the ignition is still on. You’ll need a scan tool to activate your EGR solenoid. Either visually inspect the solenoid or listen for a clicking sound. This indicates that the issue isn’t with the solenoid itself. If you can’t see the solenoid activate or hear any sound, you may need to repair or replace your EGR solenoid.

Look for any blockage in the EGR solenoid. You may need to lightly blow out any debris to ensure it activates properly. Check the ground circuit draw. Because the solenoid is attempting to activate, the voltage should be less than one amp. Any higher draw means the issue is with your ground circuit. Use a meter to check the resistance between the control circuit and ground. If the resistance isn’t infinite, then you have a short to ground on the control circuit. Find the short and repair it before checking the resistance again.

Finally, you may need to replace your EGR solenoid, wiring or even your powertrain control module. These are unlikely repairs needed for OBD-II scanner error code P0403 problem, but complete the list of common repairs.