P1437

DTC P1437 VACUUM LINE MALFUNCTION

CIRCUIT DESCRIPTION

DTC Detecting Condition:

Before the engine is started, the bypass valve remains open. When the engine is cold started, the ECM out-puts a signal to the VSV (for HC absorber and catalyst system), which open the passage between the intake manifold and the actuator, thus applying a vacuum to the actuator. As a result, the bypass valve closes. Immediately after the engine has started, the exhaust gases pass through the absorber material in with HC becomes adsorbed and stored for a certain length of time (until the temperature of the front TWC rises). Thus, the release of HC into the atmosphere is prevented when the temperature of the TWC is low.

After the TWC has warmed up, the VSV closes the passage between the intake manifold and the actuator, causing the bypass valve to open. Then, as the temperature of the rear TWC rises, the temperature of the absorber material that surrounds it also rises, and the HC starts to desorb, and becomes cleaned by the TWC.

Furthermore, this system activates the VSV when decelerating and the HC absorber has become the specified temperature, allowing the vacuum from the intake manifold to close the bypass valve in order to scavenge the HC that remains in the absorber material.

INSPECTION PROCEDURE

Step 1 - 3:

Step 4 - 6:

Step 7:

TOYOTA hand-held tester:

Step 1 - 3:

Step 4 - 6:

Step 7:

OBD II scan tool (excluding TOYOTA hand-held tester):