DTC P0406

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

General Description 

Courtesy of HONDA, U.S.A., INC.

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 powertrain control module (PCM). The EGR valve position sensor indicates the amount of valve lift, and the 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 the EGR valve position sensor output voltage is not within a specified value, the PCM detects a malfunction and stores a DTC.

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

Execution	Continuous
Sequence	None
Duration	2 seconds or more
DTC Type	Two drive cycles, MIL on
OBD Status	PASSED/FAILED/NOT COMPLETED (STILL TESTING)

Enable Conditions 

Condition
State of the engine	Running

Malfunction Threshold 

The EGR valve position sensor output voltage [EGR valve position sensor (EGR VLS)] is 4.89 V or more for at least 2 seconds.

[ ]: HDS Parameter

Possible Cause 

NOTE:  The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

• EGR valve position sensor failure
• EGR valve position sensor EGR L line short to EGR valve position sensor VCC line
• PCM internal circuit failure

Diagnosis Details 

Conditions for setting the DTC 

When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC 

The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the 12 volt battery.