Supercharger boost pressure is regulated to prevent engine and drive train damage. When the engine is operating under high boost conditions, the module limits boost pressure to 9 psi. The PCM disables boost under the following conditions:

The control module controls boost pressure by using the boost control solenoid. The boost control solenoid is a normally open valve. Under most conditions, the control module commands the boost control solenoid to operate at a 100 percent duty cycle. This keeps the solenoid valve closed and allows only inlet vacuum to control the position of the bypass valve. At idle, engine vacuum is applied to the upper side of the bypass valve actuator, counteracting spring tension to hold the bypass open. As engine load is increased, engine vacuum is decreased, causing the spring in the bypass valve actuator to overcome the applied vacuum, closing the bypass valve and allowing the boost pressure to increase. When reduced boost pressure is desired, the control module commands the boost control solenoid to operate at a 0 percent duty cycle. This opens the solenoid valve and allows boost pressure to enter the bypass valve actuator at the lower side to counteract the spring tension, opening the bypass valve and recirculating excess boost pressure back into the supercharger inlet.

Schematic Reference

Engine Controls Schematics

Description and Operation

Boost Control System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools Required

J 23738-A Mityvac

1. Review the vacuum schematics in the Boost Control System Description. Refer to Boost Control System Description .
2. Ignition OFF, visually and physically inspect the supercharger components for any of the following conditions:

Inspect the vacuum lines for:

•

Cracking

•

Loose fit

•	Improper connections

•	Improper routing

3. Inspect the following components for damage, and for proper connections, adjustments, and installation:

•	The bypass valve actuator

•	The boost control solenoid

•	The bypass valve lever

•	The bypass valve cable

4. Engine running, command the supercharger bypass (SCB) solenoid from 0-90 percent with a scan tool. Observe the operation of the bypass valve. It should move as the DC percentages are varied.
5. Verify there are no vacuum leaks at the supercharger manifold gaskets and supercharger intake plenum.

1. Ignition OFF, disconnect the boost source hose from the boost control solenoid. Connect the J 23738-A to the boost source hose.
2. Engine running, observe the gage on the J 23738-A for a reading equal to or greater than 15 in Hg.

⇒	If less than 15 in Hg, repair the boost vacuum source hose or the intake manifold port for a restriction or blockage.

3. Ignition OFF, connect the vacuum source hose to the boost solenoid.

⇒	If less than 18 in Hg, then repair the boost signal hose for a restriction or blockage.

4. Disconnect the boost signal hose from the bottom port of the bypass valve actuator and connect the J 23738-A to the boost signal hose.
5. Engine running, observe the gage on the J 23738-A for a reading of 0-1 in Hg.

⇒	If greater than the specified range, replace the boost control solenoid.

6. Engine running, command the boost control solenoid to 0 percent DC with a scan tool. Observe the gage on the J 23738-A for a reading equal to or greater than 15 in Hg.

⇒	If less than the specified range, test the boost signal hose for a restriction or blockage. If the boost signal hose tests normal, replace the boost control solenoid.

7. Disconnect the inlet vacuum signal hose from the top of the bypass valve actuator, and connect the J 23738-A to the inlet vacuum signal hose.
8. Engine running, observe the gage on the J 23738-A for a reading equal to or greater than 15 in Hg.

⇒	If less than 15 in Hg, repair the inlet vacuum signal hose or the intake manifold port for a restriction or blockage.

1. Ignition OFF, disconnect the inlet vacuum signal hose from the top of the bypass valve actuator.
2. Connect J 23738-A to the inlet vacuum signal port at the by-pass valve actuator.
3. Slowly apply 15 in Hg of vacuum while observing the bypass valve actuator. The bypass valve actuator and cable should retract.

⇒	If the bypass valve actuator and cable do not retract, inspect the bypass valve and bypass valve actuator linkage for binding, sticking, or damage. If the bypass valve, cable, and linkage operate normally, replace the bypass valve actuator.

4. Connect the inlet vacuum signal hose to the top of the bypass valve actuator.
5. Disconnect the boost signal hose from the bottom of the bypass valve actuator, and connect J 23738-A to the boost signal port on the bypass valve actuator.
6. Start and idle the engine in park.
7. Slowly apply vacuum until you reach 20 in Hg, and observe the bypass valve actuator. The bypass valve actuator should extend.

⇒	If the bypass valve actuator does not extend, inspect the bypass valve and linkage for binding, sticking, or damage. If the bypass valve and linkage operate normally, replace the bypass valve actuator.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.