OBD Code P0406

Exhaust Gas Recirculation Sensor “A” Circuit High

What’s mean?

OBD2 Code P0406 Definition:
The optical sensor provides a high resolution signal to the Powertrain Control Module (PCM) by counting pulses on the sensor disk located in the injection pump. The high resolution is one of the most important inputs by the PCM for fuel control and timing. This test monitors the number of high resolution pulses which have been missed (not detected). It’s based on a comparison between the number of pulses that were detected since the last pump cam pulse and the number of the pulses that should have occurred. There are approximately 64 high resolution pulses for every cam pulse.

Symptoms

Possible sumptoms of P0406
– Engine Light ON (or Service Engine Soon Warning Light)

Possible Causes

Possible causes of P0406
– Open or short in the optical sensor circuit – Optical sensor connector – Damaged optical sensor – Damaged PCM or ECM The Error code is generally activated on detection of the following conditions: Some high resolution pulses are missing from the optical sensor to the PCM

Possible Solutions

– If damage, repair optical sensor circuit – Replaced optical sensor – Replaced PCM or ECM