P0406 - EXHAUST GAS RECIRCULATION SENSOR "A" CIRCUIT HIGH

The design of the Exhaust Gas Recirculation (EGR) system has the objective of minimizing the combustion temperatures, allowing the emission of nitrogen oxides to be low. To do this, it sends the cylinder back to the inert exhaust gases in order to be burned with the air-fuel mixture. In this way, the inert exhaust gas burns slower.

The valve of the EGR system is controlled by the PCM (Power Train Control Module). This valve opens to let the exhaust gases flow to the cylinders.

Depending on the model, the valve can be controlled by vacuum. In this case, there is a vacuum solenoid that is controlled equally by the PCM. There are also EGR valves that are electronically controlled directly by the Powertrain Control Module (PCM).

The EGR system also has a feedback sensor known as an EVP sensor (EGR valve Position Sensor) which is responsible for informing the computer of the actual position of the EGR. The normal sensor voltage is 0.4 to 5 volts. If the EVP sensor gives a reading that is excessive for a long time, the DTC code P0406 OBD2 is set.

• Check Engine light on.
• Unstable motor.
• Increase in combustion temperatures.

This diagnostic code can be established due to:

• There may be elements in the EGR valve.
• The signal circuit of the EGR Position Sensor (EVP) may be short, it may be the battery voltage or the reference signal.
• The signal circuit cables of the EVP sensor may be defective.
• Cables of the earth circuit of the sensor EGR valve position sensor in bad condition.
• Internal failure of the EVP sensor.

Faced with the P0406 OBDII fault code, you must do the following:

• Remove the Exhaust Gas Recirculation (EGR) valve and check it for items that may be blocking it, clean it and reinstall it.
• If after doing the above the problem persists, you can block the EGR port and then start the engine. If the engine starts, you must change the EGR valve because it is stuck. But if the motor shuts down, you should check the wiring, since there must be a short circuit.
• With an automotive scanner, see the position of the EGR valve in the data flow, compare the readings with the factory specifications. If the result of this reading is correct, the problem is intermittent. If it shows 5 volts or more, there may be a signal short circuit from the EVP sensor, it also checks the ground circuit, repairs or changes as necessary.
• Change the solenoid controller of the EGR valve.
• Replace the EGR valve.