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ENRUDEPLES

P0402 — Exhaust Gas Recirculation Flow Excessive Detected

moderate

What it means

Too much exhaust gas is being recirculated into the intake, most often because the EGR valve does not close fully at idle or during warm-up. Excess inert gas displaces fresh air, so the mixture burns unstably and the engine stumbles, idles roughly or stalls when coming to a stop. The fault is detected by the DPFE sensor, the EGR position sensor or an unexpected drop in manifold vacuum.

Likely causes (most common first)

  1. EGR valve stuck open by carbon deposits or a damaged seat
  2. Torn or hardened EGR valve diaphragm, weak return spring
  3. Vacuum solenoid leaking or permanently energised, so vacuum reaches the valve at idle
  4. Faulty DPFE differential pressure sensor giving an inflated flow reading
  5. EGR position sensor out of calibration
  6. Wiring short to power in the EGR control circuit

Can you drive with it?

Short trips are possible, but the engine may stall at idle, so have it fixed without delay.

This is the generic meaning. What about your car?

The same code has different typical culprits on different engines. Tell the AI your make, model and year — it will rank the causes for your exact car and give you a check order.

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