Emissions

P0402 — Exhaust Gas Recirculation (EGR) Flow Excessive

Severity: medium Drive with care, to a shop

What P0402 means

The engine control module compares commanded and actual EGR flow. The EGR system routes a measured amount of exhaust into the intake to lower combustion temperature and NOx emissions. P0402 sets when actual flow is higher than expected, for example with an EGR valve stuck open or a sensor reading incorrectly.

Symptoms

  • Check Engine light on
  • Rough or unstable idle
  • Hesitation or stalling
  • Reduced power and acceleration
  • Worse fuel economy
  • Failed emissions test

Possible causes

  1. EGR valve stuck open or faulty
  2. Faulty DPFE or other EGR pressure/flow sensor
  3. Vacuum leak or failed EGR control solenoid
  4. Carbon buildup or clogged EGR passages
  5. Damaged EGR wiring or poor connector contact
  6. Cracked or blocked vacuum hoses (on vacuum-operated systems)

How to diagnose

  1. Scan all codes and review freeze frame data
  2. Check battery voltage and sensor supply
  3. Inspect EGR valve and sensor wiring and connectors for damage or corrosion
  4. Check vacuum lines and the control solenoid where fitted
  5. Compare commanded and actual EGR position or flow in live data
  6. Remove the EGR valve and inspect it and the passages for carbon and proper seating
  7. Test the DPFE or pressure sensor and its hoses
  8. Clear the code and road test to confirm the repair

Common fixes

  • Clean or replace the EGR valve
  • Replace the DPFE or EGR pressure sensor
  • Repair vacuum leaks and replace the solenoid or hoses
  • Clean carbon from EGR passages
  • Repair wiring and connectors

Questions and answers

What does P0402 mean?

The ECM detected more exhaust gas recirculation flow than expected. The usual causes are an EGR valve stuck open or a faulty flow sensor.

Can I drive with P0402?

For a short time, yes, but the engine may idle poorly or stall. Get it diagnosed soon.

Will cleaning the EGR valve fix it?

Often, if carbon keeps the valve from closing. If the valve or sensor has failed, it needs replacement.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.