AutoDiag

P0402

Exhaust Gas Recirculation "A" Flow Excessive Detected

Moderate· Fix soonIntermediatePowertrainGeneric, all makes

What it means

Too much exhaust gas is flowing through the EGR system, usually because the valve is stuck partly open with carbon.

Is it safe to drive?

Drivable with care. The engine may idle rough or stall, especially when stopping.

Symptoms

  • Check engine light on
  • Rough idle
  • Stalling at stops
  • Hesitation

Probable causes

Most likely first

  1. 1EGR valve stuck open with carbon
  2. 2Faulty EGR solenoid or control
  3. 3Faulty EGR position or pressure sensor

How to diagnose it

Work through these in order before buying parts

  1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
  2. 2Watch the EGR position on live data with the valve commanded closed.
  3. 3Remove and inspect the valve for carbon holding it open.
  4. 4Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

  • Clean or replace the EGR valve
  • Replace the EGR solenoid or sensor

This information is general guidance for all makes. Exact causes, specifications and procedures vary by vehicle, so confirm with your service manual or a qualified mechanic before replacing parts.