Intake Air Bypass Control Thermal Valve Test

Special Tools Required 

1. Vacuum pump gauge, 0-30 in.Hg
2. A973X-041-XXXXX

1. Start the engine, and let it idle.
   NOTE: Engine coolant temperature must be below 104°F (40°C).
2. Remove the vacuum hose (A) from the intake pipe, and connect a vacuum gauge to the hose.
   Fig 1: Removing Vacuum Hose

   Courtesy of AMERICAN HONDA MOTOR CO., INC.
3. Raise and lower the engine speed, and make sure the vacuum gauge reading changes as the rpm changes.

   If the vacuum reading changes, go to step 4.

   If the vacuum reading does not change, check for these problems:

   • Misrouted, leaking, broken, or clogged intake air bypass control thermal system vacuum lines.
   • A cracked or damage intake air bypass control thermal valve.
4. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on, then let it idle.
5. Raise and lower the engine speed, and make sure the vacuum gauge reading does not change as the rpm changes.

   If the vacuum reading changes, check for these problems:

   • Misrouted, leaking, broken, or clogged intake air bypass control thermal system.
   • A cracked or damaged intake air bypass control thermal valve.