What does the P0403 OBD-II code mean?

The P0403 code is an indication that the engine exhaust gas recirculation circuit (EGR) has malfunctioned. The engine control module (ECM) detects either a short or open circuit in the EGR vacuum control solenoid or wiring to the solenoid.

How serious is the P0403 code?

When the diagnostic code P0403 is triggered, the EGR system is disabled, rendering it inoperative, possibly causing dangerous fumes to come from your vehicle. The vehicle will also unlikely pass any type of emissions test.

What are the common symptoms of a P0403 trouble code?

When a P0403 OBD-II code is triggered, the following are the most common symptoms:

  • Check Engine Light illuminates 
  • Issues with acceleration (pre-ignition/pinging)
  • Misfiring on startup 
  • EGR system will disable
  • Engine unstable on idle 
  • Excessive fuel odor coming from the exhaust

What are the causes of a P0403 diagnostic code?

The most common causes for the P0403 trouble code being triggered are:

  • Defective EGR solenoid (common)
  • Open or short circuit the solenoid
  • EGR vacuum control solenoid is open internally or shorted
  • Failed EGR valve
  • Corrosion of the solenoid connection or losing connection
  • Defective EGR electrode
  • EGR vacuum line leak

How to diagnose a P0403 OBD-II code?

The quickest way to diagnose an OBD-II fault code is to book a diagnostic check with a trusted mechanic or garage, or use an OBD-II scanner. Following the diagnostic steps fully and correctly is important for accurate diagnosis:

  • Research to check if there are any technical service bulletins available for your vehicle’s model and make to check if there’s a known issue for your car that can help resolve the issue.
  • Scan your system for other OBD-II codes. If present, these must be resolved first.
  • Clear the fault codes, then follow this with a test drive of the car while reading the live data on an OBD-II scanner.
  • If the code persists, visually check the wiring and connections to the EGR control solenoid and the EGR temperature sensor.
  • Disconnect and check the EGR valve vacuum control solenoid for an open or short circuit in the solenoid.