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% 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.

Description and Operation

DTC Type Reference

Scan Tool Reference

Scan Tool Data List

Special Tools Required

J 23738-A Mityvac

1. Start the engine and monitor the diagnostic trouble code (DTC) information on the scan tool. If DTC P0033 is also set then diagnose it first.
2. Inspect the following items and repair any condition as necessary:

•	The vacuum lines for cracking, and loose fit

•	The bypass valve actuator for sticking, binding, or damage

•	The bypass valve for sticking, binding, or damage

•	The bypass valve linkage for binding or damage

•	The boost control solenoid for damage

3. Start the engine and command the Supercharger Boost Solenoid ON and OFF with a scan tool. The by-pass valve should open and close when commanded ON and OFF.

Important: This diagnostic assumes that the engine is in satisfactory mechanical condition and able to provide sufficient vacuum to operate the boost control system.

1. Turn OFF the ignition. Disconnect the boost signal hose from the bottom of the by-pass valve actuator, and connect J 23738-A Mityvac to the boost signal hose.
2. Start and idle the engine in park, and observe the vacuum gauge for near 0 in Hg.

⇒	If the vacuum reading is not near 0 in Hg, then replace the boost control solenoid.

3. Connect a scan tool and command the boost control solenoid OFF (0 percent duty cycle). Observe the vacuum gauge for 18 in Hg.

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

4. Turn Off the ignition, reconnect the boost signal hose to the by-pass valve actuator. Disconnect the boost source hose from the boost control solenoid, and connect J 23738-A Mityvac to the boost signal port on the boost control solenoid.
5. Start and idle the engine in park, command the boost control solenoid OFF (0 percent duty cycle) with a scan tool and observe the vacuum gauge for 18 in Hg.

⇒	If more than 18 in Hg, then replace the boost control solenoid.

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

6. Turn OFF the ignition, reconnect the boost signal hose to the by-pass valve actuator.
7. Turn OFF the ignition, disconnect the boost source hose from the boost control solenoid, and connect J 23738-A Mityvac to the boost source hose.
8. Start and idle the engine in park and observe the vacuum gauge for 15 in Hg.

⇒	If more then 15 in Hg, then replace the boost control solenoid.

⇒	If less than 15 in Hg, then repair the boost source hose for a restriction or blockage.

9. Disconnect the inlet vacuum signal hose from the top of the by-pass valve actuator, and connect J 23738-A Mityvac to the inlet vacuum signal hose.
10. Start and idle the engine in park and observe the vacuum gauge for 15 in Hg.

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

1. Turn OFF the ignition. Disconnect the inlet vacuum signal hose from the top of the by-pass valve actuator.
2. Connect J 23738-A Mityvac to the inlet vacuum signal port at the top of the by-pass valve actuator.
3. Slowly apply Vacuum until you reach 15 in Hg, and observe the by-pass valve actuator. The by-pass actuator should retract.

⇒	If the by-pass valve actuator does not retract, then inspect the by-pass valve and by-pass valve actuator linkage for binding, sticking, or damage. If NO movement then replace the by-pass valve actuator.

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

⇒	If the by-pass valve actuator does not extend, then inspect the by-pass valve and by-pass valve actuator linkage for binding, sticking, or damage. If NO movement then replace the by-pass valve actuator.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Boost Control Solenoid Replacement

Supercharger Bypass Valve Actuator Replacement