Advanced Diagnostics

Advanced Diagnostics

DTC P0406: Exhaust Gas Recirculation (EGR) Valve Position Sensor Circuit High Voltage







General Description
The exhaust gas recirculation (EGR) system reduces oxides of nitrogen (NOx). NOx is generated by high combustion temperatures. The EGR system lowers peak combustion temperature by recirculating inert exhaust gas into the air/fuel mixture, thus reducing NOx emissions. To determine the optimal amount of recirculating exhaust gas, depending on driving conditions, a command value (the amount of valve lift) is stored in the engine control module (ECM)/powertrain control module (PCM). The EGR valve position sensor indicates the amount of valve lift, and the ECM/PCM controls the EGR valve so that the amount of actual valve lift equals the command value by comparing the command value and the actual amount of valve lift. If EGR valve position sensor output voltage is not within a specified value, a malfunction is detected and a DTC is stored.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status







Enable Conditions







Malfunction Threshold
The EGR valve position sensor output voltage is 4.88 V or more for at least 2 seconds.

Diagnosis Details

Conditions for illuminating the MIL
When a malfunction is detected during the first drive cycle, a Temporary DTC is stored in the ECM/PCM memory. If the malfunction recurs during the next (second) drive cycle, the MIL comes on and the DTC and the freeze frame data are stored.

Conditions for clearing the MIL
The MIL will be cleared if the malfunction does not recur during three consecutive drive cycles in which the engine conditions are similar to the first time the malfunction was detected. The MIL, the DTC, the Temporary DTC, and the freeze frame data can be cleared by using the scan tool Clear command or by disconnecting the battery.