LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Buick >> 2002 >> Century Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 3.1L Engine >> Diagnostic Tests >> DTC P0404: EGR System >> Test Description
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Test Description

The numbers below refer to the step numbers in the diagnostic procedures.

  1. 2

    This step verifies that the malfunction is present.

  2. 3

    If DTC P0404 will only set during certain conditions, the malfunction may be intermittent. Refer to DIAGNOSTIC AIDS . If an intermittent wiring problem is not present, test for a faulty connection at PCM or EGR valve. If connections are okay, and if DTC P0404 continues to set, replace EGR valve.
scientia non olet · About LEMON Manuals