AI Diesel Tech
P0409OBD-IIEGR

Exhaust Gas Recirculation Sensor A Circuit

Common Symptoms

  • Check Engine Light illuminated
  • Rough idle or engine hesitation
  • Poor fuel economy
  • Failed emissions test
  • Reduced engine performance under load

Most Likely Root Causes

  • Faulty EGR position sensor
  • Damaged or corroded wiring harness to EGR valve
  • Poor electrical connection at EGR sensor connector
  • Carbon buildup on EGR valve affecting sensor operation
  • Failed EGR valve assembly

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Component Location

The EGR valve and position sensor are typically mounted on the intake manifold or near the throttle body area on the engine.

Manufacturer Notes

Some manufacturers integrate the EGR position sensor into the valve assembly requiring complete replacement if sensor fails.

Also diagnosing J1939 SPN/FMI codes?

Heavy-duty trucks often throw both OBD-II and J1939 faults simultaneously. AI Diesel Tech handles both protocols in a single guided session.

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