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Powertrain fault code

P0402: Exhaust Gas Recirculation "A" Flow Excessive Detected

Fix soon

Usually drivable, but rough idle, knocking or limp mode can follow.

What P0402 means

The EGR system is letting through too little or too much exhaust gas.

Common causes

  • Carbon-blocked EGR valve or passages
  • Sticking EGR valve
  • Faulty EGR position sensor or vacuum supply

What to check first

  1. Have the EGR valve inspected and cleaned.
  2. Check vacuum lines to the EGR valve (older cars).

Get P0402 explained for your car: $2.99

  • P0402 explained in full for your make and model: meaning, how urgent, likely causes and what to check, in order.
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Read your car's codes yourself, free

Plug a cheap ELM327 OBD-II adapter into the port under the dashboard and open the scan tool: Chrome or Edge on a computer with a USB adapter, or Chrome on Android with a Bluetooth LE adapter. It reads and clears codes and shows emissions readiness. It does not work on iPhone.

Open the free scan tool

Need help with P0402?

Tell us your car and what it is doing with P0402. We reply by email with what to check first, in plain words. Free.

Related codes

P0400P0401

General guidance only, not a diagnosis. A qualified mechanic should confirm the cause before you replace parts.