A P0406 code on your 2021 Honda CR-V indicates the ECM is detecting higher-than-expected voltage from the EGR position sensor circuit. This high reading prevents accurate valve position monitoring.
Understanding High Circuit Readings
High voltage from a position sensor typically indicates an open circuit condition. When the signal wire is broken or disconnected, the ECM sees the full reference voltage without the sensor's voltage-dividing effect. A sensor that has failed with high internal resistance can also cause this condition.
CR-V EGR System
The 2021 CR-V uses a 1.5L turbocharged four-cylinder engine. The EGR system helps manage combustion temperatures and emissions. The position sensor provides crucial feedback for the ECM to verify valve operation matches commands.
Diagnostic Process
Use Honda HDS to read raw sensor voltage. A stuck-high reading (near 5V) regardless of valve position confirms the problem. Disconnect the sensor connector—voltage should go to maximum with an open circuit (this is the condition you're seeing). Check the signal wire for breaks. Test sensor resistance and compare to specifications.
Repair Requirements
For wiring issues, locate and repair the open circuit. A failed sensor requires valve assembly replacement on most designs. Verify connector pins make proper contact. After repair, command the EGR valve through its range while monitoring sensor output to verify proper operation.