How Do You Tell If the Vacuum Switching Valve on a 1998 Toyota Camry Is Bad?by Walt Sampson
The vacuum switching valve (VSV) is a part of the exhaust gas recirculation (EGR) system of the 1998 Toyota Camry. The VSV is connected to the EGR valve. The function of the EGR system is to recirculate exhaust gases to the intake manifold of the engine and thereby reduce the nitrous oxide emissions of the vehicle (References 1). Detecting a bad VSV is difficult, but can be accomplished after completing a few tests.
Locate the vacuum switching valve. It has three vacuum hoses and a two-wire electrical connector attached to it. On four-cylinder engines, the VSV is located on the rear of the engine below the intake manifold. On six-cylinder engines, the VSV is under the V-Bank cover (a plate with fins), which must be unbolted using an Allen wrench, and then removed by lifting it off its retaining clips. The VSV is next to the intake manifold.
Check the resistance. Remove the electrical connector from the VSV and check the resistance across the terminals using an ohmmeter. The resistance should be 33 to 39 ohms (at an air temperature of 68 degrees). Resistance outside this range indicates that the VSV is bad (References 1).
Continuity test. Verify, using the ohmmeter, that there is no continuity between either VSV terminal and an electrical ground on the engine. Any continuity at either terminal indicates the VSV is bad.
Blow test. Remove the vacuum hoses from ports E and G. Blow air into port E and check that it comes out at port G. If it does not, the VSV is bad.
Apply voltage and blow air. Apply battery voltage across the VSV terminals using wires from the battery terminals. Blow air into port E and see if it comes out of port F. If it does not, the VSV is bad (References 1).
Things You'll Need
- Allen wrench
- Wires (with clips to connect to the battery terminals and the VSV terminals)
- Vacuum hose (to attach to port E and blow through VSV)
Walt Sampson has written technical manuals and corporate proposals since 1970. He has written for "The Denver Post" and "The Arizona Republic." Energy-conservation awards led to writing for professional magazines. Sampson has engineering degrees from the Naval Academy and the University of Michigan, and a Master of Christian Studies from Regent College.