Supercharger boost pressure is regulated to prevent engine and drive train damage. When the engine is operating under high boost conditions, the engine control module (ECM) limits boost pressure to 12 psi or less. The ECM disables boost under the following conditions:

The ECM controls boost pressure by pulse width modulation (PWM) of the boost control solenoid. The boost control solenoid is a normally open valve. Under most conditions, the ECM commands the boost control solenoid to operate at a 99-100 percent duty cycle. This keeps the boost control solenoid valve closed and allows only inlet vacuum from the supercharger plenum to the bypass valve actuator 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 valve open. When the engine load is increased, the engine vacuum is decreased, causing the spring in the bypass valve actuator to overcome the diminishing applied vacuum, closing the bypass valve and allowing the boost pressure to increase. When reduced boost pressure is desired, the ECM commands the boost control solenoid to operate at a 0-98 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.

The ECM monitors the voltage level on the boost control solenoid control circuit. Refer to Boost Control System Description for further information.

The ECM detects an improper voltage level on the boost control solenoid control circuit for more than 20 seconds.

DTC P0033 is a Type B DTC.

DTC P0033 is a Type B DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. Engine running, command the supercharger vacuum bypass valve control (SCB) solenoid, duty cycle from 0 percent to 90 percent in 10 percent increments with a scan tool. Listen and feel for a clicking at the supercharger SCB solenoid.
2. Engine running, observe the scan tool SCB Solenoid Circuit Status parameter. The reading should change from incomplete to OK when commanding the SCB solenoid.
3. Engine running, observe the DTC information with a scan tool. DTC P0033 should not set.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

1. Ignition OFF, disconnect the harness connector at the SCB solenoid.
2. Ignition ON, verify that a test lamp illuminates between the ignition supply circuit and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

3. Connect a test lamp between the control circuit and the ignition supply circuit.
4. Engine running, command the SCB solenoid duty cycle from 0 percent to 90 percent with a scan tool. The test lamp should change brightness when incrementing between the commanded states.

⇒	If the test lamp remains ON all the time, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.

⇒	If the test lamp remains OFF all the time, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, test the SCB solenoid. Refer to Component Testing for instructions.

Static Test

1. Ignition OFF, disconnect the harness connector at the SCB solenoid.
2. Test for 30-55 ohms of resistance between the control terminal and the voltage supply terminal of the SCB solenoid.

⇒	If the resistance is not within the specified range, replace the SCB solenoid.

Dynamic Test

1. Install a 3A fused jumper wire between the ignition supply circuit terminal and 12 volts. Install a jumper wire between the control terminal and ground.
2. Toggle the jumper wire between the control terminal and ground.
3. Feel and listen for the operation of the SCB solenoid.

⇒	If the function does not perform as specified, replace the SCB solenoid.

Engine running, command the supercharger vacuum SCB solenoid duty cycle from 0 percent to 100 percent in 10 percent increments with a scan tool. Listen and feel for the SCB solenoid to click.