P0403 - EXHAUST GAS RECIRCULATION CIRCUIT MALFUNCTION

The Exhaust Gas Recirculation (EGR) system is monitored by a vacuum solenoid. Once the power switch is activated, the solenoid is supplied with power. The Power Train Control Module (PCM) supervise the vacuum solenoid and the control circuit will connect to ground.

The main function of this controller is provide ground to the controller. The Powertrain Control Module (PCM) monitors each of the controllers’ circuits to determine possible faults. When one of these components is turned on by the PCM, the expected voltage in the circuit must be zero. The voltage should be high or close to the battery voltaje, if the parts are switched off. The PCM observes these two conditions before, in case you don’t see the proper voltage at that time, the DTC code P0403 OBD2 is established.

• Check engine light comes on.
• Misfiring.
• Problems in acceleration.
• At idle, the vehicle is unstable.

When the fault code P0403 OBD II is established, it means that one or more of the following faults is occurring:

• The EGR electrode may be defective.
• The resistance in the earth circuit can be excessive.
• There may be a bad connection in the cable system leading to the solenoid. Maybe there are wires worn.
• Presence of water in the solenoid cables.
• The EGR valve control solenoid may be blocked, producing excessive resistance.
• There is a loss of reference voltage to the control solenoid of the EGR valve.

The steps to follow for the correct repair of the P0403 diagnostic code are:

• With the key in the ignition position and the engine off, using an automotive scanner, activates the EGR valve control solenoid. Pay attention and if you hear a sound similar to a click, it indicates the solenoid is running.
• If you check the solenoid is running, you have to verify the current consumption in the ground circuit. Approximately, less than one ampere must be the value. If so, the problem is not constant. You should check all cables, if you find defects in them, repair them or change them as necessary.
• If the current consumption in the earth circuit is greater than that mentioned, it means that has excessive resistance. To do this, when the solenoid is activated, check if you can gently blow through it, since there may be an element that causes an obstacle, causing infinite resistance. If you can not blow, you must change the solenoid.
• If there is no lock, disconnect the solenoid and using a Digital Volt-Ohm Meter, verify the resistance between the ground and the control circuit. The result is that it must be infinite. Otherwise, there is a short circuit to ground in the control circuit. Fix it and check it again.