Diagnostic trouble code

P0402 EGR Flow Excessive

The PCM sees more EGR flow than expected.

EGR & Secondary Air Codes

Read This First

This code identifies the failed diagnostic test or circuit family. Confirm the basic checks before replacing parts, and keep freeze-frame data until the repair is verified.

Common Checks

  • Inspect for a stuck-open EGR valve.
  • Check DPFE sensor hoses and wiring on equipped cars.
  • Look for rough idle or stalling that improves when EGR is blocked for testing.

Common Repairs

  • Replace or clean a sticking EGR valve.
  • Repair DPFE hose, sensor, or wiring faults.
  • Correct vacuum-control faults that hold EGR open.

Mustang Notes

Model-Year Applicability

Listed for 1996-2010 traditional gasoline Mustang pages in this first-pass catalog. Engine, calibration, and Ford-specific codes may narrow that range as more service data is added.

Sources

  1. SAE J2012DA Digital Annex of Diagnostic Trouble Code Definitions