P0403 OBD-II Trouble Code: Exhaust Gas Recirculation Circuit Malfunction

P0403 code definition

Exhaust Gas Recirculation Circuit Malfunction

What the P0403 code means

P0403 is an OBD-II generic code that indicates that the engine control module (ECM) has detected the engine exhaust gas recirculation (EGR) circuit has malfunctioned. The ECM detected a short or open circuit in the EGR vacuum control solenoid or wiring to the solenoid.

What causes the P0403 code?

• The ECM monitors the EGR vacuum control solenoid voltage and will detect a short or open circuit to the solenoid.

• The EGR vacuum control solenoid is shorted or open internally.

• The solenoid connection is corroded and losing connections.

What are the symptoms of the P0403 code?

• The Check Engine Light will be illuminated and the code is set in ECM memory.
• The engine may have pre-ignition on acceleration.
• The engine EGR system will be disabled by the ECM.

How does a mechanic diagnose the P0403 code?

• Scans codes and documents the freeze frame data in order to verify the problem.

• Clears the engine codes and road tests the vehicle to verify whether the code comes back.

• Visually checks the wiring and connections to the EGR control solenoid along with the EGR temperature sensor.

• Disconnects and checks the EGR valve vacuum control solenoid for a short or open circuit in the solenoid.

• Checks solenoid connection for corrosion in connection.

Common mistakes when diagnosing the P0403 code

• Failing to disconnect the connection to the EGR control solenoid to check the connection for a corrosion buildup that could cause an open circuit to the ECM that could set this code.

• Failing to check the wiring harness for cut wires causing an open circuit before replacing a good solenoid.

How serious is the P0403 code?

• An EGR system that triggers this code IN the ECM will disable the EGR system and render it inoperative.

• The Check Engine Light being on will cause the vehicle to fail emission testing and may cause the engine to ping on acceleration.

What repairs can fix the P0403 code?

• Replacing the shorted or open EGR vacuum solenoid
• Replacing a corroded connector to the EGR vacuum control solenoid
• Repairing the wiring shorted to the EGR vacuum control solenoid

Additional comments for consideration regarding the P0403 code

Code P0403 is triggered when the EGR vacuum control solenoid is not making a complete and correct circuit to the ECM. When this happens, the ECM will turn off its control of the solenoid.

Need help with a P0403 code?

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