LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Buick >> 2007 >> Allure CX >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - 3.8L - DTC P0350 To P2610 >> DTC P0401 >> Circuit/System Testing
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Circuit/System Testing

IMPORTANT: You must complete the Circuit/System Verification before proceeding with Circuit/System Testing.
  1. Ignition OFF, disconnect the EGR valve harness connector.
  2. Ignition ON, connect a test lamp between B+ and the EGR low control circuit. The test lamp should illuminate.
    • If the test lamp does not illuminate, test the EGR low control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  3. Connect a test lamp between the EGR high control circuit and ground. Command the EGR valve from 0-90 percent and exit the EGR Solenoid Output Control. The test lamp should turn ON when commanded between 10-90 percent and turn OFF when commanded to 0 percent.
    • If the test lamp is ON when commanded to 0 percent, test the EGR high control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    • If the test lamp is always OFF while commanding the EGR valve from 0-90 percent, test the EGR high control circuit for an open, high resistance, or a short to ground. If the circuit tests normal, replace the ECM.
  4. If all circuits test normal, replace the EGR valve.
scientia non olet · About LEMON Manuals