2003 Honda Civic SiFACTORY OEM SERVICE PROCEDURE

EVAP Two Way Valve Test

  1. Remove the fuel fill cap.
  2. Disconnect the vapor line from the EVAP two way valve (A). Connect it to a T-Fitting from the vacuum gauge and the commercially available vacuum pump/gauge, 0-30 in. Hg (A973X-041-XXXXX or Snap-On YA4000A or equivalent)
    Fig 1: Disconnecting The Vapor Line From The EVAP Two Way Valve
    G01399662Courtesy of AMERICAN HONDA MOTOR CO., INC.
  3. Apply vacuum slowly and continuously while watching the gauge. The vacuum should stabilize momentarily at 0.8-2.1 kPa (6-16 mmHg, 0.2-0.6 in.Hg).

    If the vacuum stabilizes (valve opens) below 0.8 kPa (6 mmHg, 0.2 in.Hg) or above 2.1 kPa (16 mmHg, 0.6 in.Hg), install a new valve and retest.

  4. Move the vacuum pump hose from the vacuum fitting to the pressure fitting, and move the vacuum gauge hose from the vacuum side to the pressure side (A) as shown.
    Fig 2: Moving The Vacuum Pump Hose From The Vacuum Fitting To The Pressure Fitting, And Moving The Vacuum Gauge Hose From The Vacuum Side To The Pressure Side
    G01399663Courtesy of AMERICAN HONDA MOTOR CO., INC.
  5. Slowly pressurize the vapor line while watching the gauge. The pressure should stabilize momentarily above 1.0 kPa (8 mmHg, 0.3 in.Hg).
    • If the pressure momentarily stabilizes (valve opens) above 1.0 kPa (8 mmHg, 0.3 in.Hg), the valve is OK.
    • If the pressure stabilizes below 1.0 kPa (8 mmHg, 0.3 in.Hg), install a new valve and retest.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.